diff --git a/apps/navmeshtool/worldspacedata.cpp b/apps/navmeshtool/worldspacedata.cpp
index 04347f6c8f..e6f1dca6b0 100644
--- a/apps/navmeshtool/worldspacedata.cpp
+++ b/apps/navmeshtool/worldspacedata.cpp
@@ -264,8 +264,7 @@ namespace NavMeshTool
             const osg::Vec2i cellPosition(cell.mData.mX, cell.mData.mY);
             const std::size_t cellObjectsBegin = data.mObjects.size();
             const auto cellWorldspace = Misc::StringUtils::lowerCase(
-                (cell.isExterior() ? ESM::RefId::stringRefId(ESM::Cell::sDefaultWorldspace) : cell.mId)
-                    .serializeText());
+                (cell.isExterior() ? ESM::Cell::sDefaultWorldspaceId : cell.mId).serializeText());
             WorldspaceNavMeshInput& navMeshInput = [&]() -> WorldspaceNavMeshInput& {
                 auto it = navMeshInputs.find(cellWorldspace);
                 if (it == navMeshInputs.end())
diff --git a/apps/opencs/model/world/idtable.cpp b/apps/opencs/model/world/idtable.cpp
index 23e772afcd..b91035f758 100644
--- a/apps/opencs/model/world/idtable.cpp
+++ b/apps/opencs/model/world/idtable.cpp
@@ -337,7 +337,7 @@ std::pair<CSMWorld::UniversalId, std::string> CSMWorld::IdTable::view(int row) c
         return std::make_pair(UniversalId::Type_None, "");
 
     if (id[0] == '#')
-        id = ESM::Cell::sDefaultWorldspace;
+        id = ESM::Cell::sDefaultWorldspaceId.getValue();
 
     return std::make_pair(UniversalId(UniversalId::Type_Scene, id), hint);
 }
diff --git a/apps/opencs/view/world/regionmap.cpp b/apps/opencs/view/world/regionmap.cpp
index f7a495c9df..a2847848d0 100644
--- a/apps/opencs/view/world/regionmap.cpp
+++ b/apps/opencs/view/world/regionmap.cpp
@@ -305,7 +305,8 @@ void CSVWorld::RegionMap::view()
     }
 
     emit editRequest(
-        CSMWorld::UniversalId(CSMWorld::UniversalId::Type_Scene, ESM::Cell::sDefaultWorldspace), hint.str());
+        CSMWorld::UniversalId(CSMWorld::UniversalId::Type_Scene, ESM::Cell::sDefaultWorldspaceId.getValue()),
+        hint.str());
 }
 
 void CSVWorld::RegionMap::viewInTable()
diff --git a/apps/opencs/view/world/scenesubview.cpp b/apps/opencs/view/world/scenesubview.cpp
index ffdf1c66bf..3b3ada43b5 100644
--- a/apps/opencs/view/world/scenesubview.cpp
+++ b/apps/opencs/view/world/scenesubview.cpp
@@ -47,7 +47,7 @@ CSVWorld::SceneSubView::SceneSubView(const CSMWorld::UniversalId& id, CSMDoc::Do
     CSVRender::WorldspaceWidget* worldspaceWidget = nullptr;
     widgetType whatWidget;
 
-    if (Misc::StringUtils::ciEqual(id.getId(), ESM::Cell::sDefaultWorldspace))
+    if (Misc::StringUtils::ciEqual(id.getId(), ESM::Cell::sDefaultWorldspaceId.getValue()))
     {
         whatWidget = widget_Paged;
 
@@ -168,7 +168,8 @@ void CSVWorld::SceneSubView::cellSelectionChanged(const CSMWorld::UniversalId& i
 
 void CSVWorld::SceneSubView::cellSelectionChanged(const CSMWorld::CellSelection& selection)
 {
-    setUniversalId(CSMWorld::UniversalId(CSMWorld::UniversalId::Type_Scene, ESM::Cell::sDefaultWorldspace));
+    setUniversalId(
+        CSMWorld::UniversalId(CSMWorld::UniversalId::Type_Scene, ESM::Cell::sDefaultWorldspaceId.getValue()));
     int size = selection.getSize();
 
     std::ostringstream stream;
diff --git a/apps/openmw/mwbase/world.hpp b/apps/openmw/mwbase/world.hpp
index 71bb85c798..31a93e9201 100644
--- a/apps/openmw/mwbase/world.hpp
+++ b/apps/openmw/mwbase/world.hpp
@@ -55,6 +55,7 @@ namespace ESM
     struct ItemLevList;
     struct TimeStamp;
     class RefId;
+    struct ExteriorCellLocation;
 }
 
 namespace MWPhysics
@@ -250,10 +251,6 @@ namespace MWBase
         ///< Move to interior cell.
         ///< @param changeEvent If false, do not trigger cell change flag or detect worldspace changes
 
-        virtual void changeToExteriorCell(const ESM::Position& position, bool adjustPlayerPos, bool changeEvent = true)
-            = 0;
-        ///< Move to exterior cell.
-        ///< @param changeEvent If false, do not trigger cell change flag or detect worldspace changes
         virtual void changeToCell(
             const ESM::RefId& cellId, const ESM::Position& position, bool adjustPlayerPos, bool changeEvent = true)
             = 0;
@@ -316,9 +313,6 @@ namespace MWBase
         /// relative to \a referenceObject (but the object may be placed somewhere else if the wanted location is
         /// obstructed).
 
-        virtual void indexToPosition(int cellX, int cellY, float& x, float& y, bool centre = false) const = 0;
-        ///< Convert cell numbers to position.
-
         virtual void queueMovement(const MWWorld::Ptr& ptr, const osg::Vec3f& velocity) = 0;
         ///< Queues movement for \a ptr (in local space), to be applied in the next call to
         /// doPhysics.
diff --git a/apps/openmw/mwclass/door.cpp b/apps/openmw/mwclass/door.cpp
index 3b9aae37d4..24866fe365 100644
--- a/apps/openmw/mwclass/door.cpp
+++ b/apps/openmw/mwclass/door.cpp
@@ -17,7 +17,6 @@
 #include "../mwworld/actionteleport.hpp"
 #include "../mwworld/actiontrap.hpp"
 #include "../mwworld/cellstore.hpp"
-#include "../mwworld/cellutils.hpp"
 #include "../mwworld/containerstore.hpp"
 #include "../mwworld/customdata.hpp"
 #include "../mwworld/esmstore.hpp"
diff --git a/apps/openmw/mwgui/mapwindow.cpp b/apps/openmw/mwgui/mapwindow.cpp
index 44306c30a5..f3d3b346e4 100644
--- a/apps/openmw/mwgui/mapwindow.cpp
+++ b/apps/openmw/mwgui/mapwindow.cpp
@@ -23,7 +23,6 @@
 #include "../mwbase/world.hpp"
 
 #include "../mwworld/cellstore.hpp"
-#include "../mwworld/cellutils.hpp"
 #include "../mwworld/esmstore.hpp"
 #include "../mwworld/player.hpp"
 #include "../mwworld/worldmodel.hpp"
@@ -277,7 +276,10 @@ namespace MWGui
 
         if (!mInterior)
         {
-            cellIndex = MWWorld::positionToCellIndex(worldX, worldY);
+            ESM::ExteriorCellLocation cellPos = ESM::positionToCellIndex(worldX, worldY);
+            cellIndex.x() = cellPos.mX;
+            cellIndex.y() = cellPos.mY;
+
             nX = (worldX - cellSize * cellIndex.x()) / cellSize;
             // Image space is -Y up, cells are Y up
             nY = 1 - (worldY - cellSize * cellIndex.y()) / cellSize;
@@ -583,8 +585,8 @@ namespace MWGui
             if (!entry.mMapTexture)
             {
                 if (!mInterior)
-                    requestMapRender(
-                        &MWBase::Environment::get().getWorldModel()->getExterior(entry.mCellX, entry.mCellY));
+                    requestMapRender(&MWBase::Environment::get().getWorldModel()->getExterior(
+                        ESM::ExteriorCellLocation(entry.mCellX, entry.mCellY, ESM::Cell::sDefaultWorldspaceId)));
 
                 osg::ref_ptr<osg::Texture2D> texture = mLocalMapRender->getMapTexture(entry.mCellX, entry.mCellY);
                 if (texture)
@@ -641,7 +643,9 @@ namespace MWGui
             for (MapEntry& entry : mMaps)
             {
                 if (!entry.mMapTexture && !widgetCropped(entry.mMapWidget, mLocalMap))
-                    world->getDoorMarkers(worldModel->getExterior(entry.mCellX, entry.mCellY), doors);
+                    world->getDoorMarkers(worldModel->getExterior(ESM::ExteriorCellLocation(
+                                              entry.mCellX, entry.mCellY, ESM::Cell::sDefaultWorldspaceId)),
+                        doors);
             }
             if (doors.empty())
                 return;
diff --git a/apps/openmw/mwgui/travelwindow.cpp b/apps/openmw/mwgui/travelwindow.cpp
index 55ff9fa601..e5f840874d 100644
--- a/apps/openmw/mwgui/travelwindow.cpp
+++ b/apps/openmw/mwgui/travelwindow.cpp
@@ -15,7 +15,6 @@
 
 #include "../mwworld/actionteleport.hpp"
 #include "../mwworld/cellstore.hpp"
-#include "../mwworld/cellutils.hpp"
 #include "../mwworld/class.hpp"
 #include "../mwworld/containerstore.hpp"
 #include "../mwworld/esmstore.hpp"
@@ -126,12 +125,11 @@ namespace MWGui
         {
             std::string_view cellname = transport[i].mCellName;
             bool interior = true;
-            const osg::Vec2i cellIndex
-                = MWWorld::positionToCellIndex(transport[i].mPos.pos[0], transport[i].mPos.pos[1]);
+            const ESM::ExteriorCellLocation cellIndex
+                = ESM::positionToCellIndex(transport[i].mPos.pos[0], transport[i].mPos.pos[1]);
             if (cellname.empty())
             {
-                MWWorld::CellStore& cell
-                    = MWBase::Environment::get().getWorldModel()->getExterior(cellIndex.x(), cellIndex.y());
+                MWWorld::CellStore& cell = MWBase::Environment::get().getWorldModel()->getExterior(cellIndex);
                 cellname = MWBase::Environment::get().getWorld()->getCellName(&cell);
                 interior = false;
             }
@@ -194,8 +192,8 @@ namespace MWGui
         MWBase::Environment::get().getWindowManager()->exitCurrentGuiMode();
 
         MWBase::Environment::get().getWindowManager()->fadeScreenOut(1);
-        osg::Vec2i posCell = MWWorld::positionToCellIndex(pos.pos[0], pos.pos[1]);
-        ESM::RefId cellId = ESM::Cell::generateIdForCell(!interior, cellname, posCell.x(), posCell.y());
+        const ESM::ExteriorCellLocation posCell = ESM::positionToCellIndex(pos.pos[0], pos.pos[1]);
+        ESM::RefId cellId = ESM::Cell::generateIdForCell(!interior, cellname, posCell.mX, posCell.mY);
 
         // Teleports any followers, too.
         MWWorld::ActionTeleport action(cellId, pos, true);
diff --git a/apps/openmw/mwlua/luabindings.cpp b/apps/openmw/mwlua/luabindings.cpp
index e05466740c..0084c4a901 100644
--- a/apps/openmw/mwlua/luabindings.cpp
+++ b/apps/openmw/mwlua/luabindings.cpp
@@ -113,8 +113,10 @@ namespace MWLua
         addTimeBindings(api, context, true);
         api["getCellByName"]
             = [](std::string_view name) { return GCell{ &MWBase::Environment::get().getWorldModel()->getCell(name) }; };
-        api["getExteriorCell"]
-            = [](int x, int y) { return GCell{ &MWBase::Environment::get().getWorldModel()->getExterior(x, y) }; };
+        api["getExteriorCell"] = [](int x, int y) {
+            return GCell{ &MWBase::Environment::get().getWorldModel()->getExterior(
+                ESM::ExteriorCellLocation(x, y, ESM::Cell::sDefaultWorldspaceId)) };
+        };
         api["activeActors"] = GObjectList{ worldView->getActorsInScene() };
         api["createObject"] = [](std::string_view recordId, sol::optional<int> count) -> GObject {
             // Doesn't matter which cell to use because the new object will be in disabled state.
diff --git a/apps/openmw/mwlua/worldview.cpp b/apps/openmw/mwlua/worldview.cpp
index 9ccc1caaf8..f5699dff89 100644
--- a/apps/openmw/mwlua/worldview.cpp
+++ b/apps/openmw/mwlua/worldview.cpp
@@ -10,7 +10,6 @@
 
 #include "../mwclass/container.hpp"
 
-#include "../mwworld/cellutils.hpp"
 #include "../mwworld/class.hpp"
 #include "../mwworld/timestamp.hpp"
 #include "../mwworld/worldmodel.hpp"
diff --git a/apps/openmw/mwphysics/physicssystem.cpp b/apps/openmw/mwphysics/physicssystem.cpp
index d2076a6280..1c37ac029e 100644
--- a/apps/openmw/mwphysics/physicssystem.cpp
+++ b/apps/openmw/mwphysics/physicssystem.cpp
@@ -483,9 +483,11 @@ namespace MWPhysics
             mHeightFields.erase(heightfield);
     }
 
-    const HeightField* PhysicsSystem::getHeightField(int x, int y) const
+    const HeightField* PhysicsSystem::getHeightField(ESM::ExteriorCellLocation cellIndex) const
     {
-        const auto heightField = mHeightFields.find(std::make_pair(x, y));
+        if (ESM::isEsm4Ext(cellIndex.mWorldspace))
+            return nullptr;
+        const auto heightField = mHeightFields.find(std::make_pair(cellIndex.mX, cellIndex.mY));
         if (heightField == mHeightFields.end())
             return nullptr;
         return heightField->second.get();
diff --git a/apps/openmw/mwphysics/physicssystem.hpp b/apps/openmw/mwphysics/physicssystem.hpp
index 923ace45bb..32899dd711 100644
--- a/apps/openmw/mwphysics/physicssystem.hpp
+++ b/apps/openmw/mwphysics/physicssystem.hpp
@@ -17,6 +17,7 @@
 #include <osg/ref_ptr>
 
 #include <components/detournavigator/collisionshapetype.hpp>
+#include <components/esm/util.hpp>
 
 #include "../mwworld/ptr.hpp"
 
@@ -189,7 +190,7 @@ namespace MWPhysics
 
         void removeHeightField(int x, int y);
 
-        const HeightField* getHeightField(int x, int y) const;
+        const HeightField* getHeightField(ESM::ExteriorCellLocation cellIndex) const;
 
         bool toggleCollisionMode();
 
diff --git a/apps/openmw/mwrender/landmanager.cpp b/apps/openmw/mwrender/landmanager.cpp
index 59b9fdbde4..e7a647f348 100644
--- a/apps/openmw/mwrender/landmanager.cpp
+++ b/apps/openmw/mwrender/landmanager.cpp
@@ -18,8 +18,12 @@ namespace MWRender
         mCache = new CacheType;
     }
 
-    osg::ref_ptr<ESMTerrain::LandObject> LandManager::getLand(int x, int y)
+    osg::ref_ptr<ESMTerrain::LandObject> LandManager::getLand(ESM::ExteriorCellLocation cellIndex)
     {
+        if (ESM::isEsm4Ext(cellIndex.mWorldspace))
+            return osg::ref_ptr<ESMTerrain::LandObject>(nullptr);
+        int x = cellIndex.mX;
+        int y = cellIndex.mY;
         osg::ref_ptr<osg::Object> obj = mCache->getRefFromObjectCache(std::make_pair(x, y));
         if (obj)
             return static_cast<ESMTerrain::LandObject*>(obj.get());
diff --git a/apps/openmw/mwrender/landmanager.hpp b/apps/openmw/mwrender/landmanager.hpp
index 4c00cefe9b..1a95038eea 100644
--- a/apps/openmw/mwrender/landmanager.hpp
+++ b/apps/openmw/mwrender/landmanager.hpp
@@ -3,6 +3,7 @@
 
 #include <osg/Object>
 
+#include <components/esm/util.hpp>
 #include <components/esm3terrain/storage.hpp>
 #include <components/resource/resourcemanager.hpp>
 
@@ -20,7 +21,7 @@ namespace MWRender
         LandManager(int loadFlags);
 
         /// @note Will return nullptr if not found.
-        osg::ref_ptr<ESMTerrain::LandObject> getLand(int x, int y);
+        osg::ref_ptr<ESMTerrain::LandObject> getLand(ESM::ExteriorCellLocation cellIndex);
 
         void reportStats(unsigned int frameNumber, osg::Stats* stats) const override;
 
diff --git a/apps/openmw/mwrender/terrainstorage.cpp b/apps/openmw/mwrender/terrainstorage.cpp
index c85ee62f88..ebbe3fa18b 100644
--- a/apps/openmw/mwrender/terrainstorage.cpp
+++ b/apps/openmw/mwrender/terrainstorage.cpp
@@ -68,7 +68,7 @@ namespace MWRender
 
     osg::ref_ptr<const ESMTerrain::LandObject> TerrainStorage::getLand(int cellX, int cellY)
     {
-        return mLandManager->getLand(cellX, cellY);
+        return mLandManager->getLand(ESM::ExteriorCellLocation(cellX, cellY, ESM::Cell::sDefaultWorldspaceId));
     }
 
     const ESM::LandTexture* TerrainStorage::getLandTexture(int index, short plugin)
diff --git a/apps/openmw/mwscript/cellextensions.cpp b/apps/openmw/mwscript/cellextensions.cpp
index 1c212d5f8c..147b9a5d82 100644
--- a/apps/openmw/mwscript/cellextensions.cpp
+++ b/apps/openmw/mwscript/cellextensions.cpp
@@ -123,7 +123,10 @@ namespace MWScript
                 MWBase::World* world = MWBase::Environment::get().getWorld();
                 const MWWorld::Ptr playerPtr = world->getPlayerPtr();
 
-                world->indexToPosition(x, y, pos.pos[0], pos.pos[1], true);
+                osg::Vec2 posFromIndex
+                    = ESM::indexToPosition(ESM::ExteriorCellLocation(x, y, ESM::Cell::sDefaultWorldspaceId), true);
+                pos.pos[0] = posFromIndex.x();
+                pos.pos[1] = posFromIndex.y();
                 pos.pos[2] = 0;
 
                 pos.rot[0] = pos.rot[1] = pos.rot[2] = 0;
diff --git a/apps/openmw/mwscript/transformationextensions.cpp b/apps/openmw/mwscript/transformationextensions.cpp
index 110309ae1a..fd091711c8 100644
--- a/apps/openmw/mwscript/transformationextensions.cpp
+++ b/apps/openmw/mwscript/transformationextensions.cpp
@@ -14,7 +14,6 @@
 #include "../mwbase/world.hpp"
 
 #include "../mwworld/cellstore.hpp"
-#include "../mwworld/cellutils.hpp"
 #include "../mwworld/class.hpp"
 #include "../mwworld/manualref.hpp"
 #include "../mwworld/player.hpp"
@@ -401,8 +400,9 @@ namespace MWScript
                     store = &worldModel->getCell(cellID);
                     if (store->isExterior())
                     {
-                        const osg::Vec2i cellIndex = MWWorld::positionToCellIndex(x, y);
-                        store = &worldModel->getExterior(cellIndex.x(), cellIndex.y());
+                        const ESM::ExteriorCellLocation cellIndex
+                            = ESM::positionToCellIndex(x, y, store->getCell()->getWorldSpace());
+                        store = &worldModel->getExterior(cellIndex);
                     }
                 }
                 catch (std::exception&)
@@ -416,8 +416,9 @@ namespace MWScript
                     Log(Debug::Warning) << error;
                     if (!isPlayer)
                         return;
-                    const osg::Vec2i cellIndex = MWWorld::positionToCellIndex(x, y);
-                    store = &worldModel->getExterior(cellIndex.x(), cellIndex.y());
+                    const ESM::ExteriorCellLocation cellIndex
+                        = ESM::positionToCellIndex(x, y, store->getCell()->getWorldSpace());
+                    store = &worldModel->getExterior(cellIndex);
                 }
                 if (store)
                 {
@@ -466,15 +467,15 @@ namespace MWScript
                 {
                     world->getPlayer().setTeleported(true);
                 }
-                const osg::Vec2i cellIndex = MWWorld::positionToCellIndex(x, y);
+                const ESM::ExteriorCellLocation cellIndex
+                    = ESM::positionToCellIndex(x, y, ESM::Cell::sDefaultWorldspaceId);
 
                 // another morrowind oddity: player will be moved to the exterior cell at this location,
                 // non-player actors will move within the cell they are in.
                 MWWorld::Ptr base = ptr;
                 if (isPlayer)
                 {
-                    MWWorld::CellStore* cell
-                        = &MWBase::Environment::get().getWorldModel()->getExterior(cellIndex.x(), cellIndex.y());
+                    MWWorld::CellStore* cell = &MWBase::Environment::get().getWorldModel()->getExterior(cellIndex);
                     ptr = world->moveObject(ptr, cell, osg::Vec3(x, y, z));
                 }
                 else
@@ -567,8 +568,9 @@ namespace MWScript
                 MWWorld::CellStore* store = nullptr;
                 if (player.getCell()->isExterior())
                 {
-                    const osg::Vec2i cellIndex = MWWorld::positionToCellIndex(x, y);
-                    store = &MWBase::Environment::get().getWorldModel()->getExterior(cellIndex.x(), cellIndex.y());
+                    const ESM::ExteriorCellLocation cellIndex
+                        = ESM::positionToCellIndex(x, y, player.getCell()->getCell()->getWorldSpace());
+                    store = &MWBase::Environment::get().getWorldModel()->getExterior(cellIndex);
                 }
                 else
                     store = player.getCell();
diff --git a/apps/openmw/mwstate/statemanagerimp.cpp b/apps/openmw/mwstate/statemanagerimp.cpp
index 38bba75c05..c14a221187 100644
--- a/apps/openmw/mwstate/statemanagerimp.cpp
+++ b/apps/openmw/mwstate/statemanagerimp.cpp
@@ -563,12 +563,12 @@ void MWState::StateManager::loadGame(const Character* character, const std::file
         {
             // Cell no longer exists (i.e. changed game files), choose a default cell
             Log(Debug::Warning) << "Warning: Player character's cell no longer exists, changing to the default cell";
-            MWWorld::CellStore& cell = MWBase::Environment::get().getWorldModel()->getExterior(0, 0);
-            float x, y;
-            MWBase::Environment::get().getWorld()->indexToPosition(0, 0, x, y, false);
+            ESM::ExteriorCellLocation cellIndex(0, 0, ESM::Cell::sDefaultWorldspaceId);
+            MWWorld::CellStore& cell = MWBase::Environment::get().getWorldModel()->getExterior(cellIndex);
+            osg::Vec2 posFromIndex = ESM::indexToPosition(cellIndex, false);
             ESM::Position pos;
-            pos.pos[0] = x;
-            pos.pos[1] = y;
+            pos.pos[0] = posFromIndex.x();
+            pos.pos[1] = posFromIndex.y();
             pos.pos[2] = 0; // should be adjusted automatically (adjustPlayerPos=true)
             pos.rot[0] = 0;
             pos.rot[1] = 0;
diff --git a/apps/openmw/mwworld/actionteleport.cpp b/apps/openmw/mwworld/actionteleport.cpp
index 03efcff742..926e958e95 100644
--- a/apps/openmw/mwworld/actionteleport.cpp
+++ b/apps/openmw/mwworld/actionteleport.cpp
@@ -11,7 +11,6 @@
 #include "../mwmechanics/creaturestats.hpp"
 
 #include "../mwworld/cellstore.hpp"
-#include "../mwworld/cellutils.hpp"
 #include "../mwworld/class.hpp"
 #include "../mwworld/worldmodel.hpp"
 
diff --git a/apps/openmw/mwworld/cell.cpp b/apps/openmw/mwworld/cell.cpp
index e6a288c68c..92b6ee9fc9 100644
--- a/apps/openmw/mwworld/cell.cpp
+++ b/apps/openmw/mwworld/cell.cpp
@@ -2,8 +2,12 @@
 
 #include <components/esm3/loadcell.hpp>
 #include <components/esm4/loadcell.hpp>
+#include <components/esm4/loadwrld.hpp>
 #include <components/misc/algorithm.hpp>
 
+#include "../mwbase/environment.hpp"
+#include "esmstore.hpp"
+
 namespace MWWorld
 {
     Cell::Cell(const ESM4::Cell& cell)
@@ -26,6 +30,12 @@ namespace MWWorld
             .mFogDensity = 1.f,}
             ,mWaterHeight(cell.mWaterHeight)
     {
+        if (isExterior() && mWaterHeight == ESM4::Cell::sInvalidWaterLevel)
+        {
+            auto& worldStore = MWBase::Environment::get().getESMStore()->get<ESM4::World>();
+            const ESM4::World* cellWorld = worldStore.find(mParent);
+            mWaterHeight = cellWorld->mWaterLevel;
+        }
     }
 
     Cell::Cell(const ESM::Cell& cell)
@@ -39,7 +49,7 @@ namespace MWWorld
         , mNameID(cell.mName)
         , mRegion(cell.mRegion)
         , mId(cell.mId)
-        , mParent(ESM::RefId::stringRefId(ESM::Cell::sDefaultWorldspace))
+        , mParent(ESM::Cell::sDefaultWorldspaceId)
         , mMood{
             .mAmbiantColor = cell.mAmbi.mAmbient,
             .mDirectionalColor = cell.mAmbi.mSunlight,
@@ -48,6 +58,8 @@ namespace MWWorld
         }
         ,mWaterHeight(cell.mWater)
     {
+        if (isExterior())
+            mWaterHeight = -1.f;
     }
 
     std::string Cell::getDescription() const
@@ -65,4 +77,9 @@ namespace MWWorld
         else
             return mId;
     }
+
+    ESM::ExteriorCellLocation Cell::getExteriorCellLocation() const
+    {
+        return { mGridPos.x(), mGridPos.y(), getWorldSpace() };
+    }
 }
diff --git a/apps/openmw/mwworld/cell.hpp b/apps/openmw/mwworld/cell.hpp
index eb5a4e0de7..827b360a4b 100644
--- a/apps/openmw/mwworld/cell.hpp
+++ b/apps/openmw/mwworld/cell.hpp
@@ -5,6 +5,7 @@
 
 #include <components/esm/esmbridge.hpp>
 #include <components/esm/refid.hpp>
+#include <components/esm/util.hpp>
 
 namespace ESM
 {
@@ -48,6 +49,7 @@ namespace MWWorld
         float getWaterHeight() const { return mWaterHeight; }
         const ESM::RefId& getId() const { return mId; }
         ESM::RefId getWorldSpace() const;
+        ESM::ExteriorCellLocation getExteriorCellLocation() const;
 
     private:
         bool mIsExterior;
diff --git a/apps/openmw/mwworld/cellpreloader.cpp b/apps/openmw/mwworld/cellpreloader.cpp
index 3ba20d635e..8e5c539ae0 100644
--- a/apps/openmw/mwworld/cellpreloader.cpp
+++ b/apps/openmw/mwworld/cellpreloader.cpp
@@ -102,7 +102,8 @@ namespace MWWorld
                 try
                 {
                     mTerrain->cacheCell(mTerrainView.get(), mX, mY);
-                    mPreloadedObjects.insert(mLandManager->getLand(mX, mY));
+                    mPreloadedObjects.insert(
+                        mLandManager->getLand(ESM::ExteriorCellLocation(mX, mY, ESM::Cell::sDefaultWorldspaceId)));
                 }
                 catch (std::exception&)
                 {
diff --git a/apps/openmw/mwworld/cellref.cpp b/apps/openmw/mwworld/cellref.cpp
index dcfc7ae6b7..3e81ba1c37 100644
--- a/apps/openmw/mwworld/cellref.cpp
+++ b/apps/openmw/mwworld/cellref.cpp
@@ -10,7 +10,6 @@
 
 #include <apps/openmw/mwbase/environment.hpp>
 #include <apps/openmw/mwbase/world.hpp>
-#include <apps/openmw/mwworld/cellutils.hpp>
 #include <apps/openmw/mwworld/esmstore.hpp>
 
 namespace MWWorld
@@ -89,8 +88,8 @@ namespace MWWorld
             }
             else
             {
-                const osg::Vec2i index = positionToCellIndex(ref.mDoorDest.pos[0], ref.mDoorDest.pos[1]);
-                return ESM::RefId::esm3ExteriorCell(index.x(), index.y());
+                const auto cellPos = ESM::positionToCellIndex(ref.mDoorDest.pos[0], ref.mDoorDest.pos[1]);
+                return ESM::RefId::esm3ExteriorCell(cellPos.mX, cellPos.mY);
             }
         };
         auto esm4Visit = [&](const ESM4::Reference& ref) -> ESM::RefId {
diff --git a/apps/openmw/mwworld/cellstore.cpp b/apps/openmw/mwworld/cellstore.cpp
index 2c5ab8d3ea..f000af01e5 100644
--- a/apps/openmw/mwworld/cellstore.cpp
+++ b/apps/openmw/mwworld/cellstore.cpp
@@ -664,7 +664,7 @@ namespace MWWorld
     float CellStore::getWaterLevel() const
     {
         if (isExterior())
-            return -1;
+            return getCell()->getWaterHeight();
         return mWaterLevel;
     }
 
diff --git a/apps/openmw/mwworld/cellutils.hpp b/apps/openmw/mwworld/cellutils.hpp
deleted file mode 100644
index a7e8e88c78..0000000000
--- a/apps/openmw/mwworld/cellutils.hpp
+++ /dev/null
@@ -1,19 +0,0 @@
-#ifndef OPENMW_MWWORLD_CELLUTILS_H
-#define OPENMW_MWWORLD_CELLUTILS_H
-
-#include <components/misc/constants.hpp>
-
-#include <osg/Vec2i>
-
-#include <cmath>
-
-namespace MWWorld
-{
-    inline osg::Vec2i positionToCellIndex(float x, float y)
-    {
-        return { static_cast<int>(std::floor(x / Constants::CellSizeInUnits)),
-            static_cast<int>(std::floor(y / Constants::CellSizeInUnits)) };
-    }
-}
-
-#endif
diff --git a/apps/openmw/mwworld/esmstore.cpp b/apps/openmw/mwworld/esmstore.cpp
index ad1a3ff428..d569b155cb 100644
--- a/apps/openmw/mwworld/esmstore.cpp
+++ b/apps/openmw/mwworld/esmstore.cpp
@@ -14,6 +14,7 @@
 #include <components/misc/algorithm.hpp>
 
 #include <components/esm4/common.hpp>
+#include <components/esm4/loadwrld.hpp>
 #include <components/esm4/reader.hpp>
 #include <components/esm4/readerutils.hpp>
 #include <components/esmloader/load.hpp>
diff --git a/apps/openmw/mwworld/esmstore.hpp b/apps/openmw/mwworld/esmstore.hpp
index 004c456ff1..792ba6f46a 100644
--- a/apps/openmw/mwworld/esmstore.hpp
+++ b/apps/openmw/mwworld/esmstore.hpp
@@ -42,6 +42,7 @@ namespace ESM4
     struct Ingredient;
     struct MiscItem;
     struct Weapon;
+    struct World;
 }
 
 namespace ESM
@@ -120,7 +121,7 @@ namespace MWWorld
             Store<ESM4::Static>, Store<ESM4::Cell>, Store<ESM4::Light>, Store<ESM4::Reference>, Store<ESM4::Activator>,
             Store<ESM4::Potion>, Store<ESM4::Ammunition>, Store<ESM4::Armor>, Store<ESM4::Book>, Store<ESM4::Clothing>,
             Store<ESM4::Container>, Store<ESM4::Door>, Store<ESM4::Ingredient>, Store<ESM4::MiscItem>,
-            Store<ESM4::Weapon>>;
+            Store<ESM4::Weapon>, Store<ESM4::World>>;
 
     private:
         template <typename T>
diff --git a/apps/openmw/mwworld/scene.cpp b/apps/openmw/mwworld/scene.cpp
index 65dd36c691..027e66a88a 100644
--- a/apps/openmw/mwworld/scene.cpp
+++ b/apps/openmw/mwworld/scene.cpp
@@ -13,6 +13,7 @@
 #include <components/detournavigator/navigator.hpp>
 #include <components/detournavigator/updateguard.hpp>
 #include <components/esm/records.hpp>
+#include <components/esm3/loadcell.hpp>
 #include <components/loadinglistener/loadinglistener.hpp>
 #include <components/misc/convert.hpp>
 #include <components/misc/resourcehelpers.hpp>
@@ -39,7 +40,6 @@
 
 #include "cellpreloader.hpp"
 #include "cellstore.hpp"
-#include "cellutils.hpp"
 #include "cellvisitors.hpp"
 #include "class.hpp"
 #include "esmstore.hpp"
@@ -247,12 +247,12 @@ namespace
         return std::abs(cellPosition.first) + std::abs(cellPosition.second);
     }
 
-    bool isCellInCollection(int x, int y, MWWorld::Scene::CellStoreCollection& collection)
+    bool isCellInCollection(ESM::ExteriorCellLocation cellIndex, MWWorld::Scene::CellStoreCollection& collection)
     {
         for (auto* cell : collection)
         {
             assert(cell->getCell()->isExterior());
-            if (x == cell->getCell()->getGridX() && y == cell->getCell()->getGridY())
+            if (cellIndex == cell->getCell()->getExteriorCellLocation())
                 return true;
         }
         return false;
@@ -304,8 +304,8 @@ namespace MWWorld
     {
         if (mChangeCellGridRequest.has_value())
         {
-            changeCellGrid(mChangeCellGridRequest->mPosition, mChangeCellGridRequest->mCell.x(),
-                mChangeCellGridRequest->mCell.y(), mChangeCellGridRequest->mChangeEvent);
+            changeCellGrid(mChangeCellGridRequest->mPosition, mChangeCellGridRequest->mCellIndex,
+                mChangeCellGridRequest->mChangeEvent);
             mChangeCellGridRequest.reset();
         }
 
@@ -345,7 +345,8 @@ namespace MWWorld
 
         if (cell->getCell()->isExterior())
         {
-            if (mPhysics->getHeightField(cellX, cellY) != nullptr)
+            if (mPhysics->getHeightField(ESM::ExteriorCellLocation(cellX, cellY, cell->getCell()->getWorldSpace()))
+                != nullptr)
                 mNavigator.removeHeightfield(osg::Vec2i(cellX, cellY), navigatorUpdateGuard);
 
             mPhysics->removeHeightField(cellX, cellY);
@@ -390,10 +391,12 @@ namespace MWWorld
         const int cellX = cell.getCell()->getGridX();
         const int cellY = cell.getCell()->getGridY();
         const MWWorld::Cell& cellVariant = *cell.getCell();
+        ESM::RefId worldspace = cellVariant.getWorldSpace();
+        ESM::ExteriorCellLocation cellIndex(cellX, cellY, worldspace);
 
         if (cellVariant.isExterior())
         {
-            osg::ref_ptr<const ESMTerrain::LandObject> land = mRendering.getLandManager()->getLand(cellX, cellY);
+            osg::ref_ptr<const ESMTerrain::LandObject> land = mRendering.getLandManager()->getLand(cellIndex);
             const ESM::Land::LandData* data = land ? land->getData(ESM::Land::DATA_VHGT) : nullptr;
             const int verts = ESM::Land::LAND_SIZE;
             const int worldsize = ESM::Land::REAL_SIZE;
@@ -409,7 +412,7 @@ namespace MWWorld
                 mPhysics->addHeightField(defaultHeight.data(), cellX, cellY, worldsize, verts,
                     ESM::Land::DEFAULT_HEIGHT, ESM::Land::DEFAULT_HEIGHT, land.get());
             }
-            if (const auto heightField = mPhysics->getHeightField(cellX, cellY))
+            if (const auto heightField = mPhysics->getHeightField(cellIndex))
             {
                 const osg::Vec2i cellPosition(cellX, cellY);
                 const btVector3& origin = heightField->getCollisionObject()->getWorldTransform().getOrigin();
@@ -464,7 +467,7 @@ namespace MWWorld
 
             if (cellVariant.isExterior())
             {
-                if (const auto heightField = mPhysics->getHeightField(cellX, cellY))
+                if (const auto heightField = mPhysics->getHeightField(cellIndex))
                     mNavigator.addWater(
                         osg::Vec2i(cellX, cellY), ESM::Land::REAL_SIZE, waterLevel, navigatorUpdateGuard);
             }
@@ -506,17 +509,20 @@ namespace MWWorld
 
     osg::Vec2i Scene::getNewGridCenter(const osg::Vec3f& pos, const osg::Vec2i* currentGridCenter) const
     {
+        ESM::RefId worldspace
+            = mCurrentCell ? mCurrentCell->getCell()->getWorldSpace() : ESM::Cell::sDefaultWorldspaceId;
         if (currentGridCenter)
         {
-            float centerX, centerY;
-            mWorld.indexToPosition(currentGridCenter->x(), currentGridCenter->y(), centerX, centerY, true);
-            float distance = std::max(std::abs(centerX - pos.x()), std::abs(centerY - pos.y()));
-            const float maxDistance
-                = Constants::CellSizeInUnits / 2 + mCellLoadingThreshold; // 1/2 cell size + threshold
+            osg::Vec2 center = ESM::indexToPosition(
+                ESM::ExteriorCellLocation(currentGridCenter->x(), currentGridCenter->y(), worldspace), true);
+            float distance = std::max(std::abs(center.x() - pos.x()), std::abs(center.y() - pos.y()));
+            float cellSize = ESM::getCellSize(worldspace);
+            const float maxDistance = cellSize / 2 + mCellLoadingThreshold; // 1/2 cell size + threshold
             if (distance <= maxDistance)
                 return *currentGridCenter;
         }
-        return positionToCellIndex(pos.x(), pos.y());
+        ESM::ExteriorCellLocation cellPos = ESM::positionToCellIndex(pos.x(), pos.y(), worldspace);
+        return { cellPos.mX, cellPos.mY };
     }
 
     void Scene::playerMoved(const osg::Vec3f& pos)
@@ -531,12 +537,15 @@ namespace MWWorld
 
     void Scene::requestChangeCellGrid(const osg::Vec3f& position, const osg::Vec2i& cell, bool changeEvent)
     {
-        mChangeCellGridRequest = ChangeCellGridRequest{ position, cell, changeEvent };
+        mChangeCellGridRequest = ChangeCellGridRequest{ position,
+            ESM::ExteriorCellLocation(cell.x(), cell.y(), mCurrentCell->getCell()->getWorldSpace()), changeEvent };
     }
 
-    void Scene::changeCellGrid(const osg::Vec3f& pos, int playerCellX, int playerCellY, bool changeEvent)
+    void Scene::changeCellGrid(const osg::Vec3f& pos, ESM::ExteriorCellLocation playerCellIndex, bool changeEvent)
     {
         auto navigatorUpdateGuard = mNavigator.makeUpdateGuard();
+        int playerCellX = playerCellIndex.mX;
+        int playerCellY = playerCellIndex.mY;
 
         for (auto iter = mActiveCells.begin(); iter != mActiveCells.end();)
         {
@@ -551,12 +560,8 @@ namespace MWWorld
             else
                 unloadCell(cell, navigatorUpdateGuard.get());
         }
-
-        mNavigator.setWorldspace(Misc::StringUtils::lowerCase(mWorld.getWorldModel()
-                                                                  .getExterior(playerCellX, playerCellY)
-                                                                  .getCell()
-                                                                  ->getWorldSpace()
-                                                                  .serializeText()),
+        mNavigator.setWorldspace(
+            mWorld.getWorldModel().getExterior(playerCellIndex).getCell()->getWorldSpace().serializeText(),
             navigatorUpdateGuard.get());
         mNavigator.updateBounds(pos, navigatorUpdateGuard.get());
 
@@ -578,9 +583,9 @@ namespace MWWorld
             {
                 for (int y = playerCellY - range; y <= playerCellY + range; ++y)
                 {
-                    if (!isCellInCollection(x, y, collection))
+                    if (!isCellInCollection(ESM::ExteriorCellLocation(x, y, playerCellIndex.mWorldspace), collection))
                     {
-                        refsToLoad += mWorld.getWorldModel().getExterior(x, y).count();
+                        refsToLoad += mWorld.getWorldModel().getExterior(playerCellIndex).count();
                         cellsPositionsToLoad.emplace_back(x, y);
                     }
                 }
@@ -612,9 +617,10 @@ namespace MWWorld
 
         for (const auto& [x, y] : cellsPositionsToLoad)
         {
-            if (!isCellInCollection(x, y, mActiveCells))
+            ESM::ExteriorCellLocation indexToLoad = { x, y, playerCellIndex.mWorldspace };
+            if (!isCellInCollection(indexToLoad, mActiveCells))
             {
-                CellStore& cell = mWorld.getWorldModel().getExterior(x, y);
+                CellStore& cell = mWorld.getWorldModel().getExterior(indexToLoad);
                 loadCell(cell, loadingListener, changeEvent, pos, navigatorUpdateGuard.get());
             }
         }
@@ -623,7 +629,7 @@ namespace MWWorld
 
         navigatorUpdateGuard.reset();
 
-        CellStore& current = mWorld.getWorldModel().getExterior(playerCellX, playerCellY);
+        CellStore& current = mWorld.getWorldModel().getExterior(playerCellIndex);
         MWBase::Environment::get().getWindowManager()->changeCell(&current);
 
         if (changeEvent)
@@ -676,9 +682,9 @@ namespace MWWorld
             loadingListener->setLabel("#{OMWEngine:TestingExteriorCells} (" + std::to_string(i) + "/"
                 + std::to_string(cells.getExtSize()) + ")...");
 
-            CellStore& cell = mWorld.getWorldModel().getExterior(it->mData.mX, it->mData.mY);
-            mNavigator.setWorldspace(Misc::StringUtils::lowerCase(cell.getCell()->getWorldSpace().serializeText()),
-                navigatorUpdateGuard.get());
+            CellStore& cell = mWorld.getWorldModel().getExterior(
+                ESM::ExteriorCellLocation(it->mData.mX, it->mData.mY, ESM::Cell::sDefaultWorldspaceId));
+            mNavigator.setWorldspace(cell.getCell()->getWorldSpace().serializeText(), navigatorUpdateGuard.get());
             const osg::Vec3f position
                 = osg::Vec3f(it->mData.mX + 0.5f, it->mData.mY + 0.5f, 0) * Constants::CellSizeInUnits;
             mNavigator.updateBounds(position, navigatorUpdateGuard.get());
@@ -735,8 +741,7 @@ namespace MWWorld
                 + std::to_string(cells.getIntSize()) + ")...");
 
             CellStore& cell = mWorld.getWorldModel().getInterior(it->mName);
-            mNavigator.setWorldspace(Misc::StringUtils::lowerCase(cell.getCell()->getWorldSpace().serializeText()),
-                navigatorUpdateGuard.get());
+            mNavigator.setWorldspace(cell.getCell()->getWorldSpace().serializeText(), navigatorUpdateGuard.get());
             ESM::Position position;
             mWorld.findInteriorPosition(it->mName, position);
             mNavigator.updateBounds(position.asVec3(), navigatorUpdateGuard.get());
@@ -891,8 +896,7 @@ namespace MWWorld
 
         loadingListener->setProgressRange(cell.count());
 
-        mNavigator.setWorldspace(
-            Misc::StringUtils::lowerCase(cell.getCell()->getWorldSpace().serializeText()), navigatorUpdateGuard.get());
+        mNavigator.setWorldspace(cell.getCell()->getWorldSpace().serializeText(), navigatorUpdateGuard.get());
         mNavigator.updateBounds(position.asVec3(), navigatorUpdateGuard.get());
 
         // Load cell.
@@ -932,7 +936,8 @@ namespace MWWorld
 
         const osg::Vec2i cellIndex(current.getCell()->getGridX(), current.getCell()->getGridY());
 
-        changeCellGrid(position.asVec3(), cellIndex.x(), cellIndex.y(), changeEvent);
+        changeCellGrid(position.asVec3(),
+            ESM::ExteriorCellLocation(cellIndex.x(), cellIndex.y(), current.getCell()->getWorldSpace()), changeEvent);
 
         changePlayerCell(current, position, adjustPlayerPos);
 
@@ -1153,9 +1158,9 @@ namespace MWWorld
         int cellX, cellY;
         cellX = mCurrentGridCenter.x();
         cellY = mCurrentGridCenter.y();
+        ESM::RefId extWorldspace = mWorld.getCurrentWorldspace();
 
-        float centerX, centerY;
-        mWorld.indexToPosition(cellX, cellY, centerX, centerY, true);
+        float cellSize = ESM::getCellSize(extWorldspace);
 
         for (int dx = -halfGridSizePlusOne; dx <= halfGridSizePlusOne; ++dx)
         {
@@ -1164,20 +1169,18 @@ namespace MWWorld
                 if (dy != halfGridSizePlusOne && dy != -halfGridSizePlusOne && dx != halfGridSizePlusOne
                     && dx != -halfGridSizePlusOne)
                     continue; // only care about the outer (not yet loaded) part of the grid
+                ESM::ExteriorCellLocation cellIndex(cellX + dx, cellY + dy, extWorldspace);
+                osg::Vec2 thisCellCenter = ESM::indexToPosition(cellIndex, true);
 
-                float thisCellCenterX, thisCellCenterY;
-                mWorld.indexToPosition(cellX + dx, cellY + dy, thisCellCenterX, thisCellCenterY, true);
-
-                float dist
-                    = std::max(std::abs(thisCellCenterX - playerPos.x()), std::abs(thisCellCenterY - playerPos.y()));
+                float dist = std::max(
+                    std::abs(thisCellCenter.x() - playerPos.x()), std::abs(thisCellCenter.y() - playerPos.y()));
                 dist = std::min(dist,
-                    std::max(
-                        std::abs(thisCellCenterX - predictedPos.x()), std::abs(thisCellCenterY - predictedPos.y())));
-                float loadDist = Constants::CellSizeInUnits / 2 + Constants::CellSizeInUnits - mCellLoadingThreshold
-                    + mPreloadDistance;
+                    std::max(std::abs(thisCellCenter.x() - predictedPos.x()),
+                        std::abs(thisCellCenter.y() - predictedPos.y())));
+                float loadDist = cellSize / 2 + cellSize - mCellLoadingThreshold + mPreloadDistance;
 
                 if (dist < loadDist)
-                    preloadCell(mWorld.getWorldModel().getExterior(cellX + dx, cellY + dy));
+                    preloadCell(mWorld.getWorldModel().getExterior(cellIndex));
             }
         }
     }
@@ -1193,8 +1196,9 @@ namespace MWWorld
             {
                 for (int dy = -mHalfGridSize; dy <= mHalfGridSize; ++dy)
                 {
-                    mPreloader->preload(
-                        mWorld.getWorldModel().getExterior(x + dx, y + dy), mRendering.getReferenceTime());
+                    mPreloader->preload(mWorld.getWorldModel().getExterior(
+                                            ESM::ExteriorCellLocation(x + dx, y + dy, cell.getCell()->getWorldSpace())),
+                        mRendering.getReferenceTime());
                     if (++numpreloaded >= mPreloader->getMaxCacheSize())
                         break;
                 }
@@ -1257,12 +1261,12 @@ namespace MWWorld
     };
 
     void Scene::preloadFastTravelDestinations(const osg::Vec3f& playerPos, const osg::Vec3f& /*predictedPos*/,
-        std::vector<PositionCellGrid>&
-            exteriorPositions) // ignore predictedPos here since opening dialogue with travel service takes extra time
+        std::vector<PositionCellGrid>& exteriorPositions) // ignore predictedPos here since opening dialogue with
+                                                          // travel service takes extra time
     {
         const MWWorld::ConstPtr player = mWorld.getPlayerPtr();
         ListFastTravelDestinationsVisitor listVisitor(mPreloadDistance, player.getRefData().getPosition().asVec3());
-
+        ESM::RefId extWorldspace = mWorld.getCurrentWorldspace();
         for (MWWorld::CellStore* cellStore : mActiveCells)
         {
             cellStore->forEachType<ESM::NPC>(listVisitor);
@@ -1276,8 +1280,8 @@ namespace MWWorld
             else
             {
                 osg::Vec3f pos = dest.mPos.asVec3();
-                const osg::Vec2i cellIndex = positionToCellIndex(pos.x(), pos.y());
-                preloadCell(mWorld.getWorldModel().getExterior(cellIndex.x(), cellIndex.y()), true);
+                const ESM::ExteriorCellLocation cellIndex = ESM::positionToCellIndex(pos.x(), pos.y(), extWorldspace);
+                preloadCell(mWorld.getWorldModel().getExterior(cellIndex), true);
                 exteriorPositions.emplace_back(pos, gridCenterToBounds(getNewGridCenter(pos)));
             }
         }
diff --git a/apps/openmw/mwworld/scene.hpp b/apps/openmw/mwworld/scene.hpp
index 06b4221332..cec284a693 100644
--- a/apps/openmw/mwworld/scene.hpp
+++ b/apps/openmw/mwworld/scene.hpp
@@ -13,6 +13,7 @@
 #include <unordered_map>
 #include <vector>
 
+#include <components/esm/util.hpp>
 #include <components/misc/constants.hpp>
 
 namespace osg
@@ -79,7 +80,7 @@ namespace MWWorld
         struct ChangeCellGridRequest
         {
             osg::Vec3f mPosition;
-            osg::Vec2i mCell;
+            ESM::ExteriorCellLocation mCellIndex;
             bool mChangeEvent;
         };
 
@@ -117,7 +118,7 @@ namespace MWWorld
         osg::Vec2i mCurrentGridCenter;
 
         // Load and unload cells as necessary to create a cell grid with "X" and "Y" in the center
-        void changeCellGrid(const osg::Vec3f& pos, int playerCellX, int playerCellY, bool changeEvent = true);
+        void changeCellGrid(const osg::Vec3f& pos, ESM::ExteriorCellLocation playerCellIndex, bool changeEvent = true);
 
         void requestChangeCellGrid(const osg::Vec3f& position, const osg::Vec2i& cell, bool changeEvent = true);
 
diff --git a/apps/openmw/mwworld/store.cpp b/apps/openmw/mwworld/store.cpp
index 9936b1e999..b87cf6e445 100644
--- a/apps/openmw/mwworld/store.cpp
+++ b/apps/openmw/mwworld/store.cpp
@@ -8,6 +8,7 @@
 #include <components/esm/records.hpp>
 #include <components/esm3/esmreader.hpp>
 #include <components/esm3/esmwriter.hpp>
+#include <components/esm4/loadwrld.hpp>
 #include <components/loadinglistener/loadinglistener.hpp>
 #include <components/misc/rng.hpp>
 
@@ -1104,19 +1105,56 @@ namespace MWWorld
         return foundCell->second;
     }
 
+    const ESM4::Cell* Store<ESM4::Cell>::searchExterior(ESM::ExteriorCellLocation cellIndex) const
+    {
+        const auto foundCell = mExteriors.find(cellIndex);
+        if (foundCell == mExteriors.end())
+            return nullptr;
+        return foundCell->second;
+    }
+
     ESM4::Cell* Store<ESM4::Cell>::insert(const ESM4::Cell& item, bool overrideOnly)
     {
         auto cellPtr = TypedDynamicStore<ESM4::Cell>::insert(item, overrideOnly);
-        mCellNameIndex[cellPtr->mEditorId] = cellPtr;
+        insertCell(cellPtr);
         return cellPtr;
     }
 
     ESM4::Cell* Store<ESM4::Cell>::insertStatic(const ESM4::Cell& item)
     {
         auto cellPtr = TypedDynamicStore<ESM4::Cell>::insertStatic(item);
-        mCellNameIndex[cellPtr->mEditorId] = cellPtr;
+        insertCell(cellPtr);
         return cellPtr;
     }
+
+    void Store<ESM4::Cell>::insertCell(ESM4::Cell* cellPtr)
+    {
+        if (!cellPtr->mEditorId.empty())
+            mCellNameIndex[cellPtr->mEditorId] = cellPtr;
+        if (cellPtr->isExterior())
+        {
+            ESM::ExteriorCellLocation cellindex = { cellPtr->mX, cellPtr->mY, cellPtr->mParent };
+            if (cellPtr->mCellFlags & ESM4::Rec_Persistent)
+                mPersistentExteriors[cellindex] = cellPtr;
+            else
+                mExteriors[cellindex] = cellPtr;
+        }
+    }
+
+    void Store<ESM4::Cell>::clearDynamic()
+    {
+        for (auto& cellToDeleteIt : mDynamic)
+        {
+            ESM4::Cell& cellToDelete = cellToDeleteIt.second;
+            if (cellToDelete.isExterior())
+            {
+                mExteriors.erase({ cellToDelete.mX, cellToDelete.mY, cellToDelete.mParent });
+            }
+            if (!cellToDelete.mEditorId.empty())
+                mCellNameIndex.erase(cellToDelete.mEditorId);
+        }
+        MWWorld::TypedDynamicStore<ESM4::Cell>::clearDynamic();
+    }
 }
 
 template class MWWorld::TypedDynamicStore<ESM::Activator>;
@@ -1177,3 +1215,4 @@ template class MWWorld::TypedDynamicStore<ESM4::Light>;
 template class MWWorld::TypedDynamicStore<ESM4::Reference, ESM::FormId>;
 template class MWWorld::TypedDynamicStore<ESM4::Cell>;
 template class MWWorld::TypedDynamicStore<ESM4::Weapon>;
+template class MWWorld::TypedDynamicStore<ESM4::World>;
diff --git a/apps/openmw/mwworld/store.hpp b/apps/openmw/mwworld/store.hpp
index 79bd4df536..662fc2b558 100644
--- a/apps/openmw/mwworld/store.hpp
+++ b/apps/openmw/mwworld/store.hpp
@@ -9,6 +9,7 @@
 #include <vector>
 
 #include <components/esm/refid.hpp>
+#include <components/esm/util.hpp>
 #include <components/esm3/loadcell.hpp>
 #include <components/esm3/loaddial.hpp>
 #include <components/esm3/loadglob.hpp>
@@ -177,6 +178,7 @@ namespace MWWorld
     template <class T, class Id = ESM::RefId>
     class TypedDynamicStore : public DynamicStoreBase<Id>
     {
+    protected:
         typedef std::unordered_map<Id, T> Static;
         Static mStatic;
         /// @par mShared usually preserves the record order as it came from the content files (this
@@ -283,10 +285,16 @@ namespace MWWorld
         std::unordered_map<std::string, ESM4::Cell*, Misc::StringUtils::CiHash, Misc::StringUtils::CiEqual>
             mCellNameIndex;
 
+        std::unordered_map<ESM::ExteriorCellLocation, ESM4::Cell*> mExteriors;
+        std::unordered_map<ESM::ExteriorCellLocation, ESM4::Cell*> mPersistentExteriors;
+
     public:
         const ESM4::Cell* searchCellName(std::string_view) const;
+        const ESM4::Cell* searchExterior(ESM::ExteriorCellLocation cellIndex) const;
         ESM4::Cell* insert(const ESM4::Cell& item, bool overrideOnly = false);
         ESM4::Cell* insertStatic(const ESM4::Cell& item);
+        void insertCell(ESM4::Cell* cell);
+        void clearDynamic() override;
     };
 
     template <>
diff --git a/apps/openmw/mwworld/worldimp.cpp b/apps/openmw/mwworld/worldimp.cpp
index 8c13a9a4c0..546b564d56 100644
--- a/apps/openmw/mwworld/worldimp.cpp
+++ b/apps/openmw/mwworld/worldimp.cpp
@@ -95,7 +95,6 @@
 #include "projectilemanager.hpp"
 #include "weather.hpp"
 
-#include "cellutils.hpp"
 #include "contentloader.hpp"
 #include "esmloader.hpp"
 
@@ -353,9 +352,10 @@ namespace MWWorld
         if (bypass && !mStartCell.empty())
         {
             ESM::Position pos;
-            if (!findExteriorPosition(mStartCell, pos).empty())
+            ESM::RefId cellId = findExteriorPosition(mStartCell, pos);
+            if (!cellId.empty())
             {
-                changeToExteriorCell(pos, true);
+                changeToCell(cellId, pos, true);
                 adjustPosition(getPlayerPtr(), false);
             }
             else
@@ -379,8 +379,8 @@ namespace MWWorld
                 pos.rot[1] = 0;
                 pos.rot[2] = 0;
 
-                osg::Vec2i exteriorCellPos = positionToCellIndex(pos.pos[0], pos.pos[1]);
-                ESM::RefId cellId = ESM::RefId::esm3ExteriorCell(exteriorCellPos.x(), exteriorCellPos.y());
+                ESM::ExteriorCellLocation exteriorCellPos = ESM::positionToCellIndex(pos.pos[0], pos.pos[1]);
+                ESM::RefId cellId = ESM::RefId::esm3ExteriorCell(exteriorCellPos.mX, exteriorCellPos.mY);
                 mWorldScene->changeToExteriorCell(cellId, pos, true);
             }
         }
@@ -967,25 +967,6 @@ namespace MWWorld
         mRendering->getCamera()->instantTransition();
     }
 
-    void World::changeToExteriorCell(const ESM::Position& position, bool adjustPlayerPos, bool changeEvent)
-    {
-        mPhysics->clearQueuedMovement();
-        mDiscardMovements = true;
-
-        if (changeEvent && mCurrentWorldSpace != ESM::Cell::sDefaultWorldspace)
-        {
-            // changed worldspace
-            mProjectileManager->clear();
-            mRendering->notifyWorldSpaceChanged();
-        }
-        removeContainerScripts(getPlayerPtr());
-        osg::Vec2i exteriorCellPos = positionToCellIndex(position.pos[0], position.pos[1]);
-        ESM::RefId cellId = ESM::RefId::esm3ExteriorCell(exteriorCellPos.x(), exteriorCellPos.y());
-        mWorldScene->changeToExteriorCell(cellId, position, adjustPlayerPos, changeEvent);
-        addContainerScripts(getPlayerPtr(), getPlayerPtr().getCell());
-        mRendering->getCamera()->instantTransition();
-    }
-
     void World::changeToCell(
         const ESM::RefId& cellId, const ESM::Position& position, bool adjustPlayerPos, bool changeEvent)
     {
@@ -1263,15 +1244,17 @@ namespace MWWorld
 
     MWWorld::Ptr World::moveObject(const Ptr& ptr, const osg::Vec3f& position, bool movePhysics, bool moveToActive)
     {
-        const osg::Vec2i index = positionToCellIndex(position.x(), position.y());
-
         CellStore* cell = ptr.getCell();
-        CellStore& newCell = mWorldModel.getExterior(index.x(), index.y());
-        bool isCellActive
-            = getPlayerPtr().isInCell() && getPlayerPtr().getCell()->isExterior() && mWorldScene->isCellActive(newCell);
+        ESM::RefId worldspaceId
+            = cell->isExterior() ? cell->getCell()->getWorldSpace() : ESM::Cell::sDefaultWorldspaceId;
+        const ESM::ExteriorCellLocation index = ESM::positionToCellIndex(position.x(), position.y(), worldspaceId);
+
+        CellStore* newCell = cell->isExterior() ? &mWorldModel.getExterior(index) : nullptr;
+        bool isCellActive = getPlayerPtr().isInCell() && getPlayerPtr().getCell()->isExterior()
+            && (newCell && mWorldScene->isCellActive(*newCell));
 
         if (cell->isExterior() || (moveToActive && isCellActive && ptr.getClass().isActor()))
-            cell = &newCell;
+            cell = newCell;
 
         return moveObject(ptr, cell, position, movePhysics);
     }
@@ -1388,7 +1371,8 @@ namespace MWWorld
             && !(ptr.getClass().isPersistent(ptr) && ptr.getClass().getCreatureStats(ptr).isDeathAnimationFinished());
         if (force || !ptr.getClass().isActor() || (!isFlying(ptr) && !swims && isActorCollisionEnabled(ptr)))
         {
-            osg::Vec3f traced = mPhysics->traceDown(ptr, pos, Constants::CellSizeInUnits);
+            osg::Vec3f traced
+                = mPhysics->traceDown(ptr, pos, ESM::getCellSize(ptr.getCell()->getCell()->getWorldSpace()));
             pos.z() = std::min(pos.z(), traced.z());
         }
 
@@ -1423,9 +1407,9 @@ namespace MWWorld
             if (!mPhysics->castRay(pos, targetPos, MWPhysics::CollisionType_World | MWPhysics::CollisionType_Door).mHit)
                 break;
         }
-
         targetPos.z() += distance / 2.f; // move up a bit to get out from geometry, will snap down later
-        osg::Vec3f traced = mPhysics->traceDown(actor, targetPos, Constants::CellSizeInUnits);
+        osg::Vec3f traced
+            = mPhysics->traceDown(actor, targetPos, ESM::getCellSize(actor.getCell()->getCell()->getWorldSpace()));
         if (traced != pos)
         {
             esmPos.pos[0] = traced.x();
@@ -1509,20 +1493,6 @@ namespace MWWorld
         return placed;
     }
 
-    void World::indexToPosition(int cellX, int cellY, float& x, float& y, bool centre) const
-    {
-        const int cellSize = Constants::CellSizeInUnits;
-
-        x = static_cast<float>(cellSize * cellX);
-        y = static_cast<float>(cellSize * cellY);
-
-        if (centre)
-        {
-            x += cellSize / 2;
-            y += cellSize / 2;
-        }
-    }
-
     void World::queueMovement(const Ptr& ptr, const osg::Vec3f& velocity)
     {
         mPhysics->queueObjectMovement(ptr, velocity);
@@ -1921,6 +1891,14 @@ namespace MWWorld
         return false;
     }
 
+    ESM::RefId World::getCurrentWorldspace() const
+    {
+        const CellStore* cellStore = mWorldScene->getCurrentCell();
+        if (cellStore)
+            return cellStore->getCell()->getWorldSpace();
+        return ESM::Cell::sDefaultWorldspaceId;
+    }
+
     int World::getCurrentWeather() const
     {
         return mWeatherManager->getWeatherID();
@@ -2068,8 +2046,9 @@ namespace MWWorld
             throw std::runtime_error("copyObjectToCell(): cannot copy object to null cell");
         if (cell->isExterior())
         {
-            const osg::Vec2i index = positionToCellIndex(pos.pos[0], pos.pos[1]);
-            cell = &mWorldModel.getExterior(index.x(), index.y());
+            const ESM::ExteriorCellLocation index
+                = ESM::positionToCellIndex(pos.pos[0], pos.pos[1], cell->getCell()->getWorldSpace());
+            cell = &mWorldModel.getExterior(index);
         }
 
         MWWorld::Ptr dropped = object.getClass().copyToCell(object, *cell, pos, count);
@@ -2753,7 +2732,8 @@ namespace MWWorld
                 if (xResult.ec == std::errc::result_out_of_range || yResult.ec == std::errc::result_out_of_range)
                     throw std::runtime_error("Cell coordinates out of range.");
                 else if (xResult.ec == std::errc{} && yResult.ec == std::errc{})
-                    ext = mWorldModel.getExterior(x, y).getCell();
+                    ext = mWorldModel.getExterior(ESM::ExteriorCellLocation(x, y, ESM::Cell::sDefaultWorldspaceId))
+                              .getCell();
                 // ignore std::errc::invalid_argument, as this means that name probably refers to a interior cell
                 // instead of comma separated coordinates
             }
@@ -2763,7 +2743,9 @@ namespace MWWorld
         {
             int x = ext->getGridX();
             int y = ext->getGridY();
-            indexToPosition(x, y, pos.pos[0], pos.pos[1], true);
+            osg::Vec2 posFromIndex = indexToPosition(ESM::ExteriorCellLocation(x, y, ext->getWorldSpace()), true);
+            pos.pos[0] = posFromIndex.x();
+            pos.pos[1] = posFromIndex.y();
 
             // Note: Z pos will be adjusted by adjustPosition later
             pos.pos[2] = 0;
diff --git a/apps/openmw/mwworld/worldimp.hpp b/apps/openmw/mwworld/worldimp.hpp
index c8e9ba5bd8..0bf223f9ba 100644
--- a/apps/openmw/mwworld/worldimp.hpp
+++ b/apps/openmw/mwworld/worldimp.hpp
@@ -246,6 +246,8 @@ namespace MWWorld
 
         bool isCellQuasiExterior() const override;
 
+        ESM::RefId getCurrentWorldspace() const;
+
         void getDoorMarkers(MWWorld::CellStore& cell, std::vector<DoorMarker>& out) override;
         ///< get a list of teleport door markers for a given cell, to be displayed on the local map
 
@@ -345,11 +347,6 @@ namespace MWWorld
         ///< Move to interior cell.
         ///< @param changeEvent If false, do not trigger cell change flag or detect worldspace changes
 
-        void changeToExteriorCell(
-            const ESM::Position& position, bool adjustPlayerPos, bool changeEvent = true) override;
-        ///< Move to exterior cell.
-        ///< @param changeEvent If false, do not trigger cell change flag or detect worldspace changes
-
         void changeToCell(const ESM::RefId& cellId, const ESM::Position& position, bool adjustPlayerPos,
             bool changeEvent = true) override;
         ///< @param changeEvent If false, do not trigger cell change flag or detect worldspace changes
@@ -403,9 +400,6 @@ namespace MWWorld
 
         float getMaxActivationDistance() const override;
 
-        void indexToPosition(int cellX, int cellY, float& x, float& y, bool centre = false) const override;
-        ///< Convert cell numbers to position.
-
         void queueMovement(const Ptr& ptr, const osg::Vec3f& velocity) override;
         ///< Queues movement for \a ptr (in local space), to be applied in the next call to
         /// doPhysics.
diff --git a/apps/openmw/mwworld/worldmodel.cpp b/apps/openmw/mwworld/worldmodel.cpp
index 58f47eb8aa..e9b1cf1300 100644
--- a/apps/openmw/mwworld/worldmodel.cpp
+++ b/apps/openmw/mwworld/worldmodel.cpp
@@ -8,6 +8,7 @@
 #include <components/esm3/esmreader.hpp>
 #include <components/esm3/esmwriter.hpp>
 #include <components/esm3/loadregn.hpp>
+#include <components/esm4/loadwrld.hpp>
 #include <components/loadinglistener/loadinglistener.hpp>
 #include <components/settings/settings.hpp>
 
@@ -15,7 +16,6 @@
 #include "../mwbase/world.hpp"
 
 #include "cellstore.hpp"
-#include "cellutils.hpp"
 #include "esmstore.hpp"
 
 namespace
@@ -76,11 +76,11 @@ MWWorld::CellStore& MWWorld::WorldModel::getCellStore(const ESM::Cell* cell)
     }
     else
     {
-        std::map<std::pair<int, int>, CellStore*>::iterator result
-            = mExteriors.find(std::make_pair(cell->getGridX(), cell->getGridY()));
+        ESM::ExteriorCellLocation extIndex(cell->getGridX(), cell->getGridY(), ESM::Cell::sDefaultWorldspaceId);
+        std::map<ESM::ExteriorCellLocation, CellStore*>::iterator result = mExteriors.find(extIndex);
 
         if (result == mExteriors.end())
-            result = mExteriors.emplace(std::make_pair(cell->getGridX(), cell->getGridY()), cellStore).first;
+            result = mExteriors.emplace(extIndex, cellStore).first;
 
         return *result->second;
     }
@@ -160,33 +160,57 @@ MWWorld::WorldModel::WorldModel(const MWWorld::ESMStore& store, ESM::ReadersCach
 {
 }
 
-MWWorld::CellStore& MWWorld::WorldModel::getExterior(int x, int y)
+MWWorld::CellStore& MWWorld::WorldModel::getExterior(ESM::ExteriorCellLocation cellIndex)
 {
-    std::map<std::pair<int, int>, CellStore*>::iterator result = mExteriors.find(std::make_pair(x, y));
+    std::map<ESM::ExteriorCellLocation, CellStore*>::iterator result;
+
+    result = mExteriors.find(cellIndex);
 
     if (result == mExteriors.end())
     {
-        const ESM::Cell* cell = mStore.get<ESM::Cell>().search(x, y);
+        if (!ESM::isEsm4Ext(cellIndex.mWorldspace))
+        {
+            const ESM::Cell* cell = mStore.get<ESM::Cell>().search(cellIndex.mX, cellIndex.mY);
+
+            if (cell == nullptr)
+            {
+                // Cell isn't predefined. Make one on the fly.
+                ESM::Cell record;
+                record.mData.mFlags = ESM::Cell::HasWater;
+                record.mData.mX = cellIndex.mX;
+                record.mData.mY = cellIndex.mY;
+                record.mWater = 0;
+                record.mMapColor = 0;
+                record.updateId();
+
+                cell = MWBase::Environment::get().getESMStore()->insert(record);
+            }
 
-        if (!cell)
+            CellStore* cellStore
+                = &mCells.emplace(cell->mId, CellStore(MWWorld::Cell(*cell), mStore, mReaders)).first->second;
+            result = mExteriors.emplace(cellIndex, cellStore).first;
+        }
+        else
         {
-            // Cell isn't predefined. Make one on the fly.
-            ESM::Cell record;
-            record.mData.mFlags = ESM::Cell::HasWater;
-            record.mData.mX = x;
-            record.mData.mY = y;
-            record.mWater = 0;
-            record.mMapColor = 0;
-            record.updateId();
-
-            cell = MWBase::Environment::get().getESMStore()->insert(record);
+            const Store<ESM4::Cell>& cell4Store = mStore.get<ESM4::Cell>();
+            bool exteriorExists = mStore.get<ESM4::World>().search(cellIndex.mWorldspace) != nullptr;
+            const ESM4::Cell* cell = cell4Store.searchExterior(cellIndex);
+            if (!exteriorExists)
+                throw std::runtime_error("Exterior ESM4 world is not found: " + cellIndex.mWorldspace.toDebugString());
+            if (cell == nullptr)
+            {
+                ESM4::Cell record;
+                record.mParent = cellIndex.mWorldspace;
+                record.mX = cellIndex.mX;
+                record.mY = cellIndex.mY;
+                record.mCellFlags = !ESM4::CELL_Interior;
+                cell = MWBase::Environment::get().getESMStore()->insert(record);
+            }
+            CellStore* cellStore
+                = &mCells.emplace(cell->mId, CellStore(MWWorld::Cell(*cell), mStore, mReaders)).first->second;
+            result = mExteriors.emplace(cellIndex, cellStore).first;
         }
-
-        CellStore* cellStore
-            = &mCells.emplace(cell->mId, CellStore(MWWorld::Cell(*cell), mStore, mReaders)).first->second;
-        result = mExteriors.emplace(std::make_pair(x, y), cellStore).first;
     }
-
     if (result->second->getState() != CellStore::State_Loaded)
     {
         result->second->load();
@@ -232,7 +256,8 @@ MWWorld::CellStore& MWWorld::WorldModel::getCell(const ESM::RefId& id)
         return result->second;
 
     if (const auto* exteriorId = id.getIf<ESM::ESM3ExteriorCellRefId>())
-        return getExterior(exteriorId->getX(), exteriorId->getY());
+        return getExterior(
+            ESM::ExteriorCellLocation(exteriorId->getX(), exteriorId->getY(), ESM::Cell::sDefaultWorldspaceId));
 
     const ESM4::Cell* cell4 = mStore.get<ESM4::Cell>().search(id);
     CellStore* newCellStore = nullptr;
@@ -249,7 +274,8 @@ MWWorld::CellStore& MWWorld::WorldModel::getCell(const ESM::RefId& id)
     {
         std::pair<int, int> coord
             = std::make_pair(newCellStore->getCell()->getGridX(), newCellStore->getCell()->getGridY());
-        mExteriors.emplace(coord, newCellStore);
+        ESM::ExteriorCellLocation extIndex = { coord.first, coord.second, newCellStore->getCell()->getWorldSpace() };
+        mExteriors.emplace(extIndex, newCellStore);
     }
     else
     {
@@ -293,7 +319,7 @@ MWWorld::CellStore& MWWorld::WorldModel::getCell(std::string_view name)
     if (!cell)
         throw std::runtime_error(std::string("Can't find cell with name ") + std::string(name));
 
-    return getExterior(cell->getGridX(), cell->getGridY());
+    return getExterior(ESM::ExteriorCellLocation(cell->getGridX(), cell->getGridY(), ESM::Cell::sDefaultWorldspaceId));
 }
 
 MWWorld::CellStore& MWWorld::WorldModel::getCellByPosition(
@@ -301,8 +327,11 @@ MWWorld::CellStore& MWWorld::WorldModel::getCellByPosition(
 {
     if (cellInSameWorldSpace && !cellInSameWorldSpace->isExterior())
         return *cellInSameWorldSpace;
-    const osg::Vec2i cellIndex = positionToCellIndex(pos.x(), pos.y());
-    return getExterior(cellIndex.x(), cellIndex.y());
+    ESM::RefId exteriorWorldspace
+        = cellInSameWorldSpace ? cellInSameWorldSpace->getCell()->getWorldSpace() : ESM::Cell::sDefaultWorldspaceId;
+    const ESM::ExteriorCellLocation cellIndex = ESM::positionToCellIndex(pos.x(), pos.y(), exteriorWorldspace);
+
+    return getExterior(cellIndex);
 }
 
 MWWorld::Ptr MWWorld::WorldModel::getPtr(const ESM::RefId& name, CellStore& cell)
@@ -342,8 +371,7 @@ MWWorld::Ptr MWWorld::WorldModel::getPtr(const ESM::RefId& name)
     // Then check cells that are already listed
     // Search in reverse, this is a workaround for an ambiguous chargen_plank reference in the vanilla game.
     // there is one at -22,16 and one at -2,-9, the latter should be used.
-    for (std::map<std::pair<int, int>, CellStore*>::reverse_iterator iter = mExteriors.rbegin();
-         iter != mExteriors.rend(); ++iter)
+    for (auto iter = mExteriors.rbegin(); iter != mExteriors.rend(); ++iter)
     {
         Ptr ptr = getPtrAndCache(name, *iter->second);
         if (!ptr.isEmpty())
diff --git a/apps/openmw/mwworld/worldmodel.hpp b/apps/openmw/mwworld/worldmodel.hpp
index c9c7cf52ea..b90a063c69 100644
--- a/apps/openmw/mwworld/worldmodel.hpp
+++ b/apps/openmw/mwworld/worldmodel.hpp
@@ -7,6 +7,7 @@
 #include <unordered_map>
 #include <variant>
 
+#include <components/esm/util.hpp>
 #include <components/misc/algorithm.hpp>
 
 #include "cellstore.hpp"
@@ -42,7 +43,8 @@ namespace MWWorld
         ESM::ReadersCache& mReaders;
         mutable std::unordered_map<ESM::RefId, CellStore> mCells;
         mutable std::map<std::string, CellStore*, Misc::StringUtils::CiComp> mInteriors;
-        mutable std::map<std::pair<int, int>, CellStore*> mExteriors;
+
+        mutable std::map<ESM::ExteriorCellLocation, CellStore*> mExteriors;
         IdCache mIdCache;
         std::size_t mIdCacheIndex = 0;
         std::unordered_map<ESM::RefNum, Ptr> mPtrIndex;
@@ -63,7 +65,7 @@ namespace MWWorld
 
         void clear();
 
-        CellStore& getExterior(int x, int y);
+        CellStore& getExterior(ESM::ExteriorCellLocation cellIndex);
         CellStore& getInterior(std::string_view name);
         CellStore& getCell(std::string_view name); // interior or named exterior
         CellStore& getCell(const ESM::RefId& Id);
diff --git a/apps/openmw_test_suite/mwworld/test_store.cpp b/apps/openmw_test_suite/mwworld/test_store.cpp
index aea74fab71..6a038af9dc 100644
--- a/apps/openmw_test_suite/mwworld/test_store.cpp
+++ b/apps/openmw_test_suite/mwworld/test_store.cpp
@@ -20,6 +20,7 @@
 #include <components/esm4/loadligh.hpp>
 #include <components/esm4/loadrefr.hpp>
 #include <components/esm4/loadstat.hpp>
+#include <components/esm4/loadwrld.hpp>
 #include <components/esm4/reader.hpp>
 #include <components/esm4/readerutils.hpp>
 #include <components/files/configurationmanager.hpp>
diff --git a/components/esm/util.cpp b/components/esm/util.cpp
new file mode 100644
index 0000000000..30a477641e
--- /dev/null
+++ b/components/esm/util.cpp
@@ -0,0 +1,16 @@
+#include "util.hpp"
+
+osg::Vec2 ESM::indexToPosition(const ESM::ExteriorCellLocation& cellIndex, bool centre)
+{
+    const int cellSize = ESM::getCellSize(cellIndex.mWorldspace);
+
+    float x = static_cast<float>(cellSize * cellIndex.mX);
+    float y = static_cast<float>(cellSize * cellIndex.mY);
+
+    if (centre)
+    {
+        x += cellSize / 2;
+        y += cellSize / 2;
+    }
+    return osg::Vec2(x, y);
+}
diff --git a/components/esm/util.hpp b/components/esm/util.hpp
index b1a40bd015..6edf087854 100644
--- a/components/esm/util.hpp
+++ b/components/esm/util.hpp
@@ -1,9 +1,16 @@
 #ifndef OPENMW_ESM_UTIL_H
 #define OPENMW_ESM_UTIL_H
+#include <cmath>
 
 #include <osg/Quat>
+#include <osg/Vec2>
+#include <osg/Vec2i>
 #include <osg/Vec3f>
 
+#include <components/esm/refid.hpp>
+#include <components/esm3/loadcell.hpp>
+#include <components/misc/constants.hpp>
+
 namespace ESM
 {
 
@@ -42,6 +49,66 @@ namespace ESM
         operator osg::Vec3f() const { return osg::Vec3f(mValues[0], mValues[1], mValues[2]); }
     };
 
+    struct ExteriorCellLocation
+    {
+        int mX, mY;
+        ESM::RefId mWorldspace;
+
+        ExteriorCellLocation(int x, int y, ESM::RefId worldspace)
+            : mX(x)
+            , mY(y)
+            , mWorldspace(worldspace)
+        {
+        }
+
+        bool operator==(const ExteriorCellLocation& other) const
+        {
+            return mX == other.mX && mY == other.mY && mWorldspace == other.mWorldspace;
+        }
+
+        bool operator<(const ExteriorCellLocation& other) const
+        {
+            return std::make_tuple(mX, mY, mWorldspace) < std::make_tuple(other.mX, other.mY, other.mWorldspace);
+        }
+    };
+
+    inline bool isEsm4Ext(ESM::RefId worldspaceId)
+    {
+        return worldspaceId != ESM::Cell::sDefaultWorldspaceId;
+    }
+
+    inline int getCellSize(ESM::RefId worldspaceId)
+    {
+
+        return isEsm4Ext(worldspaceId) ? Constants::ESM4CellSizeInUnits : Constants::CellSizeInUnits;
+    }
+
+    inline ESM::ExteriorCellLocation positionToCellIndex(
+        float x, float y, ESM::RefId worldspaceId = ESM::Cell::sDefaultWorldspaceId)
+    {
+        const float cellSize = getCellSize(worldspaceId);
+        return { static_cast<int>(std::floor(x / cellSize)), static_cast<int>(std::floor(y / cellSize)), worldspaceId };
+    }
+
+    osg::Vec2 indexToPosition(const ESM::ExteriorCellLocation& cellIndex, bool centre = false);
+    ///< Convert cell numbers to position.
+}
+
+namespace std
+{
+    template <>
+    struct hash<ESM::ExteriorCellLocation>
+    {
+        std::size_t operator()(const ESM::ExteriorCellLocation& toHash) const
+        {
+            // Compute individual hash values for first,
+            // second and third and combine them using XOR
+            // and bit shifting:
+
+            return ((hash<int>()(toHash.mX) ^ (hash<int>()(toHash.mY) << 1)) >> 1)
+                ^ (hash<ESM::RefId>()(toHash.mWorldspace) << 1);
+        }
+    };
 }
 
 #endif
diff --git a/components/esm3/loadcell.cpp b/components/esm3/loadcell.cpp
index 73fd8967bd..5a328d8f03 100644
--- a/components/esm3/loadcell.cpp
+++ b/components/esm3/loadcell.cpp
@@ -39,7 +39,7 @@ namespace ESM
 
 namespace ESM
 {
-    const std::string Cell::sDefaultWorldspace = "sys::default";
+    const StringRefId Cell::sDefaultWorldspaceId = StringRefId("sys::default");
 
     // Some overloaded compare operators.
     bool operator==(const MovedCellRef& ref, const RefNum& refNum)
diff --git a/components/esm3/loadcell.hpp b/components/esm3/loadcell.hpp
index c889a5a620..3d33c7c370 100644
--- a/components/esm3/loadcell.hpp
+++ b/components/esm3/loadcell.hpp
@@ -66,7 +66,7 @@ namespace ESM
      */
     struct Cell
     {
-        static const std::string sDefaultWorldspace;
+        static const ESM::StringRefId sDefaultWorldspaceId;
 
         constexpr static RecNameInts sRecordId = REC_CELL;
 
diff --git a/components/esm4/loadcell.cpp b/components/esm4/loadcell.cpp
index 22d9a1035d..21f50ff9d9 100644
--- a/components/esm4/loadcell.cpp
+++ b/components/esm4/loadcell.cpp
@@ -33,6 +33,7 @@
 #include <cassert>
 #include <cfloat> // FLT_MAX for gcc
 #include <iostream> // FIXME: debug only
+#include <limits>
 #include <stdexcept>
 
 #include "grouptype.hpp"
@@ -41,6 +42,8 @@
 
 #include <components/esm/refid.hpp>
 
+float ESM4::Cell::sInvalidWaterLevel = -200000.f;
+
 // TODO: Try loading only EDID and XCLC (along with mFormId, mFlags and mParent)
 //
 // But, for external cells we may be scanning the whole record since we don't know if there is
@@ -55,7 +58,7 @@ void ESM4::Cell::load(ESM4::Reader& reader)
     mId = ESM::RefId::formIdRefId(mFormId);
     mFlags = reader.hdr().record.flags;
     mParent = ESM::RefId::formIdRefId(reader.currWorld());
-
+    mWaterHeight = sInvalidWaterLevel;
     reader.clearCellGrid(); // clear until XCLC FIXME: somehow do this automatically?
 
     // Sometimes cell 0,0 does not have an XCLC sub record (e.g. ToddLand 000009BF)
@@ -76,6 +79,7 @@ void ESM4::Cell::load(ESM4::Reader& reader)
     reader.setCurrCell(mFormId); // save for LAND (and other children) to access later
     std::uint32_t esmVer = reader.esmVersion();
     bool isFONV = esmVer == ESM::VER_132 || esmVer == ESM::VER_133 || esmVer == ESM::VER_134;
+    bool isSkyrim = (esmVer == ESM::VER_170 || esmVer == ESM::VER_094);
 
     while (reader.getSubRecordHeader())
     {
@@ -237,7 +241,11 @@ void ESM4::Cell::load(ESM4::Reader& reader)
                 throw std::runtime_error("ESM4::CELL::load - Unknown subrecord " + ESM::printName(subHdr.typeId));
         }
     }
-
+    if (isSkyrim) // Skyrim seems to have broken water level records. But the subrecord exists so it
+                  // shouldn't be skipped.
+    {
+        mWaterHeight = sInvalidWaterLevel;
+    }
     mReaderContext = reader.getContext();
 }
 
diff --git a/components/esm4/loadcell.hpp b/components/esm4/loadcell.hpp
index 97abb88751..5fd32a598d 100644
--- a/components/esm4/loadcell.hpp
+++ b/components/esm4/loadcell.hpp
@@ -107,6 +107,8 @@ namespace ESM4
         int getGridX() const { return mX; }
         int getGridY() const { return mY; }
         bool isExterior() const { return !(mCellFlags & CELL_Interior); }
+
+        static float sInvalidWaterLevel;
     };
 }
 
diff --git a/components/esm4/loadwrld.cpp b/components/esm4/loadwrld.cpp
index f421a8e7ff..cc16ab4fa7 100644
--- a/components/esm4/loadwrld.cpp
+++ b/components/esm4/loadwrld.cpp
@@ -34,8 +34,8 @@
 
 void ESM4::World::load(ESM4::Reader& reader)
 {
-    mFormId = reader.hdr().record.getFormId();
-    reader.adjustFormId(mFormId);
+    FormId formid = reader.hdr().record.getFormId();
+    reader.adjustFormId(formid);
     mFlags = reader.hdr().record.flags;
 
     // It should be possible to save the current world formId automatically while reading in
@@ -45,7 +45,8 @@ void ESM4::World::load(ESM4::Reader& reader)
     // Alternatively it may be possible to figure it out by examining the group headers, but
     // apparently the label field is not reliable so the parent world formid may have been
     // corrupted by the use of ignore flag (TODO: should check to verify).
-    reader.setCurrWorld(mFormId); // save for CELL later
+    reader.setCurrWorld(formid); // save for CELL later
+    mId = ESM::FormIdRefId(formid);
 
     std::uint32_t subSize = 0; // for XXXX sub record
 
diff --git a/components/esm4/loadwrld.hpp b/components/esm4/loadwrld.hpp
index f5ba010ba8..7dc42cd035 100644
--- a/components/esm4/loadwrld.hpp
+++ b/components/esm4/loadwrld.hpp
@@ -34,6 +34,9 @@
 #include "formid.hpp"
 #include "grid.hpp"
 
+#include <components/esm/defs.hpp>
+#include <components/esm/refid.hpp>
+
 namespace ESM4
 {
     class Reader;
@@ -81,7 +84,7 @@ namespace ESM4
             float initialPitch;
         };
 
-        FormId mFormId; // from the header
+        ESM::RefId mId; // from the header
         std::uint32_t mFlags; // from the header, see enum type RecordFlag for details
 
         std::string mEditorId;
@@ -129,6 +132,7 @@ namespace ESM4
 
         void load(ESM4::Reader& reader);
         // void save(ESM4::Writer& writer) const;
+        static constexpr ESM::RecNameInts sRecordId = ESM::REC_WRLD4;
     };
 }
 
diff --git a/components/misc/constants.hpp b/components/misc/constants.hpp
index deb47a7667..545db87094 100644
--- a/components/misc/constants.hpp
+++ b/components/misc/constants.hpp
@@ -23,6 +23,7 @@ namespace Constants
 
     // Size of one exterior cell in game units
     constexpr int CellSizeInUnits = 8192;
+    constexpr int ESM4CellSizeInUnits = 4096;
 
     // Size of active cell grid in cells (it is a square with the (2 * CellGridRadius + 1) cells side)
     constexpr int CellGridRadius = 1;