diff --git a/src/am_map.cpp b/src/am_map.cpp
index 312e4b9018..e621425903 100644
--- a/src/am_map.cpp
+++ b/src/am_map.cpp
@@ -1831,6 +1831,8 @@ void AM_drawGrid (int color)
 	mline_t ml;
 	double minlen, extx, exty;
 	double minx, miny;
+	auto bmaporgx = level.blockmap.bmaporgx;
+	auto bmaporgy = level.blockmap.bmaporgy;
 
 	// [RH] Calculate a minimum for how long the grid lines should be so that
 	// they cover the screen at any rotation.
@@ -1843,12 +1845,12 @@ void AM_drawGrid (int color)
 
 	// Figure out start of vertical gridlines
 	start = minx - extx;
-	start = ceil((start - bmaporgx) / MAPBLOCKUNITS) * MAPBLOCKUNITS + bmaporgx;
+	start = ceil((start - bmaporgx) / FBlockmap::MAPBLOCKUNITS) * FBlockmap::MAPBLOCKUNITS + bmaporgx;
 
 	end = minx + minlen - extx;
 
 	// draw vertical gridlines
-	for (x = start; x < end; x += MAPBLOCKUNITS)
+	for (x = start; x < end; x += FBlockmap::MAPBLOCKUNITS)
 	{
 		ml.a.x = x;
 		ml.b.x = x;
@@ -1864,11 +1866,11 @@ void AM_drawGrid (int color)
 
 	// Figure out start of horizontal gridlines
 	start = miny - exty;
-	start = ceil((start - bmaporgy) / MAPBLOCKUNITS) * MAPBLOCKUNITS + bmaporgy;
+	start = ceil((start - bmaporgy) / FBlockmap::MAPBLOCKUNITS) * FBlockmap::MAPBLOCKUNITS + bmaporgy;
 	end = miny + minlen - exty;
 
 	// draw horizontal gridlines
-	for (y=start; y<end; y+=MAPBLOCKUNITS)
+	for (y=start; y<end; y+=FBlockmap::MAPBLOCKUNITS)
 	{
 		ml.a.x = minx - extx;
 		ml.b.x = ml.a.x + minlen;
diff --git a/src/g_levellocals.h b/src/g_levellocals.h
index 2deb98f94e..b52d866f9f 100644
--- a/src/g_levellocals.h
+++ b/src/g_levellocals.h
@@ -4,6 +4,7 @@
 #include "g_level.h"
 #include "r_defs.h"
 #include "portal.h"
+#include "p_blockmap.h"
 
 struct FLevelLocals
 {
@@ -46,6 +47,8 @@ struct FLevelLocals
 	TArray<FSectorPortal> sectorPortals;
 	TArray<zone_t>	Zones;
 
+	FBlockmap blockmap;
+
 	// These are copies of the loaded map data that get used by the savegame code to skip unaltered fields
 	// Without such a mechanism the savegame format would become too slow and large because more than 80-90% are normally still unaltered.
 	TArray<sector_t>	loadsectors;
diff --git a/src/p_blockmap.h b/src/p_blockmap.h
index e6474b4ea2..992f2d223a 100644
--- a/src/p_blockmap.h
+++ b/src/p_blockmap.h
@@ -22,30 +22,73 @@ struct FBlockNode
 	static FBlockNode *FreeBlocks;
 };
 
-extern int*				blockmaplump;	// offsets in blockmap are from here
+// BLOCKMAP
+// Created from axis aligned bounding box
+// of the map, a rectangular array of
+// blocks of size 128x128.
+// Used to speed up collision detection
+// by spatial subdivision in 2D.
+//
 
-extern int*				blockmap;
-extern int				bmapwidth;
-extern int				bmapheight; 	// in mapblocks
-extern double			bmaporgx;
-extern double			bmaporgy;		// origin of block map
-extern FBlockNode**		blocklinks; 	// for thing chains
-
-										// mapblocks are used to check movement
-										// against lines and things
-enum
+struct FBlockmap
 {
-	MAPBLOCKUNITS = 128
+	int*				blockmaplump;	// offsets in blockmap are from here
+
+	int*				blockmap;
+	int					bmapwidth;
+	int					bmapheight; 	// in mapblocks
+	double				bmaporgx;
+	double				bmaporgy;		// origin of block map
+	FBlockNode**		blocklinks; 	// for thing chains
+
+	// mapblocks are used to check movement
+	// against lines and things
+	enum
+	{
+		MAPBLOCKUNITS = 128
+	};
+
+	inline int GetBlockX(double xpos)
+	{
+		return int((xpos - bmaporgx) / MAPBLOCKUNITS);
+	}
+
+	inline int GetBlockY(double ypos)
+	{
+		return int((ypos - bmaporgy) / MAPBLOCKUNITS);
+	}
+
+	inline bool isValidBlock(int x, int y) const
+	{
+		return ((unsigned int)x < (unsigned int)bmapwidth &&
+			(unsigned int)y < (unsigned int)bmapheight);
+	}
+
+	inline int *GetLines(int x, int y) const
+	{
+		// There is an extra entry at the beginning of every block.
+		// Apparently, id had originally intended for it to be used
+		// to keep track of things, but the final code does not do that.
+		int offset = y*bmapwidth + x;
+		return blockmaplump + *(blockmap + offset) + 1;
+	}
+
+	bool FBlockmap::VerifyBlockMap(int count);
+
+	void Clear()
+	{
+		if (blockmaplump != NULL)
+		{
+			delete[] blockmaplump;
+			blockmaplump = NULL;
+		}
+		if (blocklinks != NULL)
+		{
+			delete[] blocklinks;
+			blocklinks = NULL;
+		}
+	}
+
 };
 
-inline int GetBlockX(double xpos)
-{
-	return int((xpos - bmaporgx) / MAPBLOCKUNITS);
-}
-
-inline int GetBlockY(double ypos)
-{
-	return int((ypos - bmaporgy) / MAPBLOCKUNITS);
-}
-
 #endif
diff --git a/src/p_enemy.cpp b/src/p_enemy.cpp
index 91d99791dd..8aed0370e5 100644
--- a/src/p_enemy.cpp
+++ b/src/p_enemy.cpp
@@ -1434,7 +1434,7 @@ AActor *LookForTIDInBlock (AActor *lookee, int index, void *extparams)
 	AActor *link;
 	AActor *other;
 	
-	for (block = blocklinks[index]; block != NULL; block = block->NextActor)
+	for (block = level.blockmap.blocklinks[index]; block != NULL; block = block->NextActor)
 	{
 		link = block->Me;
 
@@ -1613,7 +1613,7 @@ AActor *LookForEnemiesInBlock (AActor *lookee, int index, void *extparam)
 	AActor *other;
 	FLookExParams *params = (FLookExParams *)extparam;
 	
-	for (block = blocklinks[index]; block != NULL; block = block->NextActor)
+	for (block = level.blockmap.blocklinks[index]; block != NULL; block = block->NextActor)
 	{
 		link = block->Me;
 
diff --git a/src/p_maputl.cpp b/src/p_maputl.cpp
index ca2f14d10e..fc31d60caa 100644
--- a/src/p_maputl.cpp
+++ b/src/p_maputl.cpp
@@ -322,16 +322,15 @@ bool AActor::FixMapthingPos()
 {
 	sector_t *secstart = P_PointInSectorBuggy(X(), Y());
 
-	int blockx = GetBlockX(X());
-	int blocky = GetBlockY(Y());
+	int blockx = level.blockmap.GetBlockX(X());
+	int blocky = level.blockmap.GetBlockY(Y());
 	bool success = false;
 
-	if ((unsigned int)blockx < (unsigned int)bmapwidth &&
-		(unsigned int)blocky < (unsigned int)bmapheight)
+	if (level.blockmap.isValidBlock(blockx, blocky))
 	{
 		int *list;
 
-		for (list = blockmaplump + blockmap[blocky*bmapwidth + blockx] + 1; *list != -1; ++list)
+		for (list = level.blockmap.GetLines(blockx, blocky); *list != -1; ++list)
 		{
 			line_t *ldef = &level.lines[*list];
 
@@ -487,25 +486,25 @@ void AActor::LinkToWorld(FLinkContext *ctx, bool spawningmapthing, sector_t *sec
 		{
 			DVector3 pos = i==-1? Pos() : PosRelative(check[i] & ~FPortalGroupArray::FLAT);
 
-			int x1 = GetBlockX(pos.X - radius);
-			int x2 = GetBlockX(pos.X + radius);
-			int y1 = GetBlockY(pos.Y - radius);
-			int y2 = GetBlockY(pos.Y + radius);
+			int x1 = level.blockmap.GetBlockX(pos.X - radius);
+			int x2 = level.blockmap.GetBlockX(pos.X + radius);
+			int y1 = level.blockmap.GetBlockY(pos.Y - radius);
+			int y2 = level.blockmap.GetBlockY(pos.Y + radius);
 
-			if (x1 >= bmapwidth || x2 < 0 || y1 >= bmapheight || y2 < 0)
+			if (x1 >= level.blockmap.bmapwidth || x2 < 0 || y1 >= level.blockmap.bmapheight || y2 < 0)
 			{ // thing is off the map
 			}
 			else
 			{ // [RH] Link into every block this actor touches, not just the center one
 				x1 = MAX(0, x1);
 				y1 = MAX(0, y1);
-				x2 = MIN(bmapwidth - 1, x2);
-				y2 = MIN(bmapheight - 1, y2);
+				x2 = MIN(level.blockmap.bmapwidth - 1, x2);
+				y2 = MIN(level.blockmap.bmapheight - 1, y2);
 				for (int y = y1; y <= y2; ++y)
 				{
 					for (int x = x1; x <= x2; ++x)
 					{
-						FBlockNode **link = &blocklinks[y*bmapwidth + x];
+						FBlockNode **link = &level.blockmap.blocklinks[y*level.blockmap.bmapwidth + x];
 						FBlockNode *node = FBlockNode::Create(this, x, y, this->Sector->PortalGroup);
 
 						// Link in to block
@@ -580,7 +579,7 @@ FBlockNode *FBlockNode::Create (AActor *who, int x, int y, int group)
 	{
 		block = new FBlockNode;
 	}
-	block->BlockIndex = x + y*bmapwidth;
+	block->BlockIndex = x + y*level.blockmap.bmapwidth;
 	block->Me = who;
 	block->NextActor = NULL;
 	block->PrevActor = NULL;
@@ -624,10 +623,10 @@ FBlockLinesIterator::FBlockLinesIterator(int _minx, int _miny, int _maxx, int _m
 void FBlockLinesIterator::init(const FBoundingBox &box)
 {
 	validcount++;
-	maxy = GetBlockY(box.Top());
-	miny = GetBlockY(box.Bottom());
-	maxx = GetBlockX(box.Right());
-	minx = GetBlockX(box.Left());
+	maxy = level.blockmap.GetBlockY(box.Top());
+	miny = level.blockmap.GetBlockY(box.Bottom());
+	maxx = level.blockmap.GetBlockX(box.Right());
+	minx = level.blockmap.GetBlockX(box.Left());
 	Reset();
 }
 
@@ -646,16 +645,13 @@ void FBlockLinesIterator::StartBlock(int x, int y)
 { 
 	curx = x; 
 	cury = y; 
-	if (x >= 0 && y >= 0 && x < bmapwidth && y <bmapheight)
+	if (level.blockmap.isValidBlock(x, y))
 	{
-		int offset = y*bmapwidth + x;
+		int offset = y*level.blockmap.bmapwidth + x;
 		polyLink = PolyBlockMap? PolyBlockMap[offset] : NULL;
 		polyIndex = 0;
 
-		// There is an extra entry at the beginning of every block.
-		// Apparently, id had originally intended for it to be used
-		// to keep track of things, but the final code does not do that.
-		list = blockmaplump + *(blockmap + offset) + 1;
+		list = level.blockmap.GetLines(x, y);
 	}
 	else
 	{
@@ -994,10 +990,10 @@ FBlockThingsIterator::FBlockThingsIterator(int _minx, int _miny, int _maxx, int
 
 void FBlockThingsIterator::init(const FBoundingBox &box)
 {
-	maxy = GetBlockY(box.Top());
-	miny = GetBlockY(box.Bottom());
-	maxx = GetBlockX(box.Right());
-	minx = GetBlockX(box.Left());
+	maxy = level.blockmap.GetBlockY(box.Top());
+	miny = level.blockmap.GetBlockY(box.Bottom());
+	maxx = level.blockmap.GetBlockX(box.Right());
+	minx = level.blockmap.GetBlockX(box.Left());
 	ClearHash();
 	Reset();
 }
@@ -1021,13 +1017,13 @@ void FBlockThingsIterator::ClearHash()
 //
 //===========================================================================
 
-void FBlockThingsIterator::StartBlock(int x, int y) 
-{ 
-	curx = x; 
-	cury = y; 
-	if (x >= 0 && y >= 0 && x < bmapwidth && y <bmapheight)
+void FBlockThingsIterator::StartBlock(int x, int y)
+{
+	curx = x;
+	cury = y;
+	if (level.blockmap.isValidBlock(x, y))
 	{
-		block = blocklinks[y*bmapwidth + x];
+		block = level.blockmap.blocklinks[y*level.blockmap.bmapwidth + x];
 	}
 	else
 	{
@@ -1075,10 +1071,10 @@ AActor *FBlockThingsIterator::Next(bool centeronly)
 			if (centeronly)
 			{
 				// Block boundaries for compatibility mode
-				double blockleft = (curx * MAPBLOCKUNITS) + bmaporgx;
-				double blockright = blockleft + MAPBLOCKUNITS;
-				double blockbottom = (cury * MAPBLOCKUNITS) + bmaporgy;
-				double blocktop = blockbottom + MAPBLOCKUNITS;
+				double blockleft = (curx * FBlockmap::MAPBLOCKUNITS) + level.blockmap.bmaporgx;
+				double blockright = blockleft + FBlockmap::MAPBLOCKUNITS;
+				double blockbottom = (cury * FBlockmap::MAPBLOCKUNITS) + level.blockmap.bmaporgy;
+				double blocktop = blockbottom + FBlockmap::MAPBLOCKUNITS;
 
 				// only return actors with the center in this block
 				if (me->X() >= blockleft && me->X() < blockright &&
@@ -1618,15 +1614,15 @@ void FPathTraverse::init(double x1, double y1, double x2, double y2, int flags,
 		y2 += y1;
 	}
 
-	x1 -= bmaporgx;
-	y1 -= bmaporgy;
-	xt1 = x1 / MAPBLOCKUNITS;
-	yt1 = y1 / MAPBLOCKUNITS;
+	x1 -= level.blockmap.bmaporgx;
+	y1 -= level.blockmap.bmaporgy;
+	xt1 = x1 / FBlockmap::MAPBLOCKUNITS;
+	yt1 = y1 / FBlockmap::MAPBLOCKUNITS;
 
-	x2 -= bmaporgx;
-	y2 -= bmaporgy;
-	xt2 = x2 / MAPBLOCKUNITS;
-	yt2 = y2 / MAPBLOCKUNITS;
+	x2 -= level.blockmap.bmaporgx;
+	y2 -= level.blockmap.bmaporgy;
+	xt2 = x2 / FBlockmap::MAPBLOCKUNITS;
+	yt2 = y2 / FBlockmap::MAPBLOCKUNITS;
 
 	mapx = xs_FloorToInt(xt1);
 	mapy = xs_FloorToInt(yt1);
@@ -1834,7 +1830,7 @@ FPathTraverse::~FPathTraverse()
 // P_RoughMonsterSearch
 //
 // Searches though the surrounding mapblocks for monsters/players
-//		distance is in MAPBLOCKUNITS
+//		distance is in FBlockmap::MAPBLOCKUNITS
 //===========================================================================
 
 AActor *P_BlockmapSearch (AActor *mo, int distance, AActor *(*check)(AActor*, int, void *), void *params)
@@ -1849,12 +1845,14 @@ AActor *P_BlockmapSearch (AActor *mo, int distance, AActor *(*check)(AActor*, in
 	int finalStop;
 	int count;
 	AActor *target;
+	int bmapwidth = level.blockmap.bmapwidth;
+	int bmapheight = level.blockmap.bmapheight;
 
-	startX = GetBlockX(mo->X());
-	startY = GetBlockY(mo->Y());
+	startX = level.blockmap.GetBlockX(mo->X());
+	startY = level.blockmap.GetBlockY(mo->Y());
 	validcount++;
 	
-	if (startX >= 0 && startX < bmapwidth && startY >= 0 && startY < bmapheight)
+	if (level.blockmap.isValidBlock(startX, startY))
 	{
 		if ( (target = check (mo, startY*bmapwidth+startX, params)) )
 		{ // found a target right away
@@ -1945,7 +1943,7 @@ static AActor *RoughBlockCheck (AActor *mo, int index, void *param)
 
 	FBlockNode *link;
 
-	for (link = blocklinks[index]; link != NULL; link = link->NextActor)
+	for (link = level.blockmap.blocklinks[index]; link != NULL; link = link->NextActor)
 	{
 		if (link->Me != mo)
 		{
diff --git a/src/p_secnodes.cpp b/src/p_secnodes.cpp
index 346f5ff8e7..f0c7eb32f5 100644
--- a/src/p_secnodes.cpp
+++ b/src/p_secnodes.cpp
@@ -388,11 +388,11 @@ void AActor::UpdateRenderSectorList()
 		ClearRenderLineList();
 		if (PortalBlockmap.containsLines && Pos().XY() != OldRenderPos.XY())
 		{
-			int bx = GetBlockX(X());
-			int by = GetBlockY(Y());
+			int bx = level.blockmap.GetBlockX(X());
+			int by = level.blockmap.GetBlockY(Y());
 			FBoundingBox bb(X(), Y(), MIN(radius*1.5, 128.));	// Don't go further than 128 map units, even for large actors
 			// Are there any portals near the actor's position?
-			if (bx >= 0 && by >= 0 && bx < bmapwidth && by < bmapheight && PortalBlockmap(bx, by).neighborContainsLines)
+			if (level.blockmap.isValidBlock(bx, by) && PortalBlockmap(bx, by).neighborContainsLines)
 			{
 				// Go through the entire list. In most cases this is faster than setting up a blockmap iterator
 				for (auto &p : linePortals)
diff --git a/src/p_setup.cpp b/src/p_setup.cpp
index e334a272be..796b557762 100644
--- a/src/p_setup.cpp
+++ b/src/p_setup.cpp
@@ -136,34 +136,6 @@ sidei_t *sidetemp;
 
 TArray<int>		linemap;
 
-// BLOCKMAP
-// Created from axis aligned bounding box
-// of the map, a rectangular array of
-// blocks of size 256x256.
-// Used to speed up collision detection
-// by spatial subdivision in 2D.
-//
-// Blockmap size.
-int 			bmapwidth;
-int 			bmapheight; 	// size in mapblocks
-
-int				*blockmap;		// int for larger maps ([RH] Made int because BOOM does)
-int				*blockmaplump;	// offsets in blockmap are from here	
-
-double	 		bmaporgx;		// origin of block map
-double	 		bmaporgy;
-
-FBlockNode**	blocklinks;		// for thing chains
-
-
-// REJECT
-// For fast sight rejection.
-// Speeds up enemy AI by skipping detailed
-//	LineOf Sight calculation.
-// Without special effect, this could be
-//	used as a PVS lookup as well.
-//
-
 bool		ForceNodeBuild;
 
 static void P_AllocateSideDefs (MapData *map, int count);
@@ -2868,10 +2840,10 @@ static void P_CreateBlockMap ()
 	CreatePackedBlockmap (BlockMap, BlockLists, bmapwidth, bmapheight);
 	delete[] BlockLists;
 
-	blockmaplump = new int[BlockMap.Size()];
+	level.blockmap.blockmaplump = new int[BlockMap.Size()];
 	for (unsigned int ii = 0; ii < BlockMap.Size(); ++ii)
 	{
-		blockmaplump[ii] = BlockMap[ii];
+		level.blockmap.blockmaplump[ii] = BlockMap[ii];
 	}
 }
 
@@ -2882,7 +2854,7 @@ static void P_CreateBlockMap ()
 //
 // haleyjd 03/04/10: do verification on validity of blockmap.
 //
-static bool P_VerifyBlockMap(int count)
+bool FBlockmap::VerifyBlockMap(int count)
 {
 	int x, y;
 	int *maxoffs = blockmaplump + count;
@@ -2905,7 +2877,7 @@ static bool P_VerifyBlockMap(int count)
 			// check that block offset is in bounds
 			if(blockoffset >= maxoffs)
 			{
-				Printf(PRINT_HIGH, "P_VerifyBlockMap: block offset overflow\n");
+				Printf(PRINT_HIGH, "VerifyBlockMap: block offset overflow\n");
 				return false;
 			}
 
@@ -2914,7 +2886,7 @@ static bool P_VerifyBlockMap(int count)
 			// check that list offset is in bounds
 			if(offset < 4 || offset >= count)
 			{
-				Printf(PRINT_HIGH, "P_VerifyBlockMap: list offset overflow\n");
+				Printf(PRINT_HIGH, "VerifyBlockMap: list offset overflow\n");
 				return false;
 			}
 
@@ -2926,7 +2898,7 @@ static bool P_VerifyBlockMap(int count)
 				// we have overflowed the lump?
 				if(tmplist >= maxoffs)
 				{
-					Printf(PRINT_HIGH, "P_VerifyBlockMap: open blocklist\n");
+					Printf(PRINT_HIGH, "VerifyBlockMap: open blocklist\n");
 					return false;
 				}
 				if(*tmplist == -1) // found -1
@@ -2938,7 +2910,7 @@ static bool P_VerifyBlockMap(int count)
 			// to be on the safe side.
 			if (*list != 0)
 			{
-				Printf(PRINT_HIGH, "P_VerifyBlockMap: first entry is not 0.\n");
+				Printf(PRINT_HIGH, "VerifyBlockMap: first entry is not 0.\n");
 				return false;
 			}
 
@@ -2947,7 +2919,7 @@ static bool P_VerifyBlockMap(int count)
 			{
 				if((unsigned)*tmplist >= level.lines.Size())
 				{
-					Printf(PRINT_HIGH, "P_VerifyBlockMap: index >= numlines\n");
+					Printf(PRINT_HIGH, "VerifyBlockMap: index >= numlines\n");
 					return false;
 				}
 			}
@@ -2986,26 +2958,26 @@ void P_LoadBlockMap (MapData * map)
 		int i;
 
 		count/=2;
-		blockmaplump = new int[count];
+		level.blockmap.blockmaplump = new int[count];
 
 		// killough 3/1/98: Expand wad blockmap into larger internal one,
 		// by treating all offsets except -1 as unsigned and zero-extending
 		// them. This potentially doubles the size of blockmaps allowed,
 		// because Doom originally considered the offsets as always signed.
 
-		blockmaplump[0] = LittleShort(wadblockmaplump[0]);
-		blockmaplump[1] = LittleShort(wadblockmaplump[1]);
-		blockmaplump[2] = (uint32_t)(LittleShort(wadblockmaplump[2])) & 0xffff;
-		blockmaplump[3] = (uint32_t)(LittleShort(wadblockmaplump[3])) & 0xffff;
+		level.blockmap.blockmaplump[0] = LittleShort(wadblockmaplump[0]);
+		level.blockmap.blockmaplump[1] = LittleShort(wadblockmaplump[1]);
+		level.blockmap.blockmaplump[2] = (uint32_t)(LittleShort(wadblockmaplump[2])) & 0xffff;
+		level.blockmap.blockmaplump[3] = (uint32_t)(LittleShort(wadblockmaplump[3])) & 0xffff;
 
 		for (i = 4; i < count; i++)
 		{
 			short t = LittleShort(wadblockmaplump[i]);          // killough 3/1/98
-			blockmaplump[i] = t == -1 ? (uint32_t)0xffffffff : (uint32_t) t & 0xffff;
+			level.blockmap.blockmaplump[i] = t == -1 ? (uint32_t)0xffffffff : (uint32_t) t & 0xffff;
 		}
 		delete[] data;
 
-		if (!P_VerifyBlockMap(count))
+		if (!level.blockmap.VerifyBlockMap(count))
 		{
 			DPrintf (DMSG_SPAMMY, "Generating BLOCKMAP\n");
 			P_CreateBlockMap();
@@ -3013,16 +2985,16 @@ void P_LoadBlockMap (MapData * map)
 
 	}
 
-	bmaporgx = blockmaplump[0];
-	bmaporgy = blockmaplump[1];
-	bmapwidth = blockmaplump[2];
-	bmapheight = blockmaplump[3];
+	level.blockmap.bmaporgx = level.blockmap.blockmaplump[0];
+	level.blockmap.bmaporgy = level.blockmap.blockmaplump[1];
+	level.blockmap.bmapwidth = level.blockmap.blockmaplump[2];
+	level.blockmap.bmapheight = level.blockmap.blockmaplump[3];
 
 	// clear out mobj chains
-	count = bmapwidth*bmapheight;
-	blocklinks = new FBlockNode *[count];
-	memset (blocklinks, 0, count*sizeof(*blocklinks));
-	blockmap = blockmaplump+4;
+	count = level.blockmap.bmapwidth*level.blockmap.bmapheight;
+	level.blockmap.blocklinks = new FBlockNode *[count];
+	memset (level.blockmap.blocklinks, 0, count*sizeof(*level.blockmap.blocklinks));
+	level.blockmap.blockmap = level.blockmap.blockmaplump+4;
 }
 
 //
@@ -3432,20 +3404,11 @@ void P_FreeLevelData ()
 	level.gamesubsectors.Reset();
 	level.rejectmatrix.Clear();
 	level.Zones.Clear();
+	level.blockmap.Clear();
 
-	if (blockmaplump != NULL)
-	{
-		delete[] blockmaplump;
-		blockmaplump = NULL;
-	}
-	if (blocklinks != NULL)
-	{
-		delete[] blocklinks;
-		blocklinks = NULL;
-	}
 	if (PolyBlockMap != NULL)
 	{
-		for (int i = bmapwidth*bmapheight-1; i >= 0; --i)
+		for (int i = level.blockmap.bmapwidth*level.blockmap.bmapheight-1; i >= 0; --i)
 		{
 			polyblock_t *link = PolyBlockMap[i];
 			while (link != NULL)
diff --git a/src/p_sight.cpp b/src/p_sight.cpp
index 238a73ef25..c7e1dea75f 100644
--- a/src/p_sight.cpp
+++ b/src/p_sight.cpp
@@ -470,7 +470,7 @@ int SightCheck::P_SightBlockLinesIterator (int x, int y)
 	unsigned int i;
 	extern polyblock_t **PolyBlockMap;
 
-	offset = y*bmapwidth+x;
+	offset = y*level.blockmap.bmapwidth+x;
 
 	// if any of the previous blocks may contain a portal we may abort the collection of lines here, but we may not abort the sight check.
 	// (We still try to delay activating this for as long as possible.)
@@ -498,9 +498,7 @@ int SightCheck::P_SightBlockLinesIterator (int x, int y)
 		polyLink = polyLink->next;
 	}
 
-	offset = *(blockmap + offset);
-
-	for (list = blockmaplump + offset + 1; *list != -1; list++)
+	for (list = level.blockmap.GetLines(x, y); *list != -1; list++)
 	{
 		if (!P_SightCheckLine (&level.lines[*list]))
 		{
@@ -655,15 +653,15 @@ bool SightCheck::P_SightPathTraverse ()
 		portals.Push({ 0, topslope, bottomslope, sector_t::floor, lastsector->GetOppositePortalGroup(sector_t::floor) });
 	}
 
-	x1 -= bmaporgx;
-	y1 -= bmaporgy;
-	xt1 = x1 / MAPBLOCKUNITS;
-	yt1 = y1 / MAPBLOCKUNITS;
+	x1 -= level.blockmap.bmaporgx;
+	y1 -= level.blockmap.bmaporgy;
+	xt1 = x1 / FBlockmap::MAPBLOCKUNITS;
+	yt1 = y1 / FBlockmap::MAPBLOCKUNITS;
 
-	x2 -= bmaporgx;
-	y2 -= bmaporgy;
-	xt2 = x2 / MAPBLOCKUNITS;
-	yt2 = y2 / MAPBLOCKUNITS;
+	x2 -= level.blockmap.bmaporgx;
+	y2 -= level.blockmap.bmaporgy;
+	xt2 = x2 / FBlockmap::MAPBLOCKUNITS;
+	yt2 = y2 / FBlockmap::MAPBLOCKUNITS;
 
 	mapx = xs_FloorToInt(xt1);
 	mapy = xs_FloorToInt(yt1);
@@ -741,7 +739,7 @@ bool SightCheck::P_SightPathTraverse ()
 	{
 		// end traversing when reaching the end of the blockmap
 		// an early out is not possible because with portals a trace can easily land outside the map's bounds.
-		if (mapx < 0 || mapx >= bmapwidth || mapy < 0 || mapy >= bmapheight)
+		if (level.blockmap.isValidBlock(mapx, mapy))
 		{
 			break;
 		}
diff --git a/src/po_man.cpp b/src/po_man.cpp
index 5baa90be60..0a8948b232 100644
--- a/src/po_man.cpp
+++ b/src/po_man.cpp
@@ -1069,10 +1069,10 @@ void FPolyObj::UnLinkPolyobj ()
 	// remove the polyobj from each blockmap section
 	for(j = bbox[BOXBOTTOM]; j <= bbox[BOXTOP]; j++)
 	{
-		index = j*bmapwidth;
+		index = j*level.blockmap.bmapwidth;
 		for(i = bbox[BOXLEFT]; i <= bbox[BOXRIGHT]; i++)
 		{
-			if(i >= 0 && i < bmapwidth && j >= 0 && j < bmapheight)
+			if(i >= 0 && i < level.blockmap.bmapwidth && j >= 0 && j < level.blockmap.bmapheight)
 			{
 				link = PolyBlockMap[index+i];
 				while(link != NULL && link->polyobj != this)
@@ -1105,13 +1105,15 @@ bool FPolyObj::CheckMobjBlocking (side_t *sd)
 	line_t *ld;
 	bool blocked;
 	bool performBlockingThrust;
+	int bmapwidth = level.blockmap.bmapwidth;
+	int bmapheight = level.blockmap.bmapheight;
 
 	ld = sd->linedef;
 
-	top = GetBlockY(ld->bbox[BOXTOP]);
-	bottom = GetBlockY(ld->bbox[BOXBOTTOM]);
-	left = GetBlockX(ld->bbox[BOXLEFT]);
-	right = GetBlockX(ld->bbox[BOXRIGHT]);
+	top = level.blockmap.GetBlockY(ld->bbox[BOXTOP]);
+	bottom = level.blockmap.GetBlockY(ld->bbox[BOXBOTTOM]);
+	left = level.blockmap.GetBlockX(ld->bbox[BOXLEFT]);
+	right = level.blockmap.GetBlockX(ld->bbox[BOXRIGHT]);
 
 	blocked = false;
 	checker.Clear();
@@ -1129,7 +1131,7 @@ bool FPolyObj::CheckMobjBlocking (side_t *sd)
 	{
 		for (i = left; i <= right; i++)
 		{
-			for (block = blocklinks[j+i]; block != NULL; block = block->NextActor)
+			for (block = level.blockmap.blocklinks[j+i]; block != NULL; block = block->NextActor)
 			{
 				mobj = block->Me;
 				for (k = (int)checker.Size()-1; k >= 0; --k)
@@ -1230,6 +1232,8 @@ void FPolyObj::LinkPolyobj ()
 {
 	polyblock_t **link;
 	polyblock_t *tempLink;
+	int bmapwidth = level.blockmap.bmapwidth;
+	int bmapheight = level.blockmap.bmapheight;
 
 	// calculate the polyobj bbox
 	Bounds.ClearBox();
@@ -1242,10 +1246,10 @@ void FPolyObj::LinkPolyobj ()
 		vt = Sidedefs[i]->linedef->v2;
 		Bounds.AddToBox(vt->fPos());
 	}
-	bbox[BOXRIGHT] = GetBlockX(Bounds.Right());
-	bbox[BOXLEFT] = GetBlockX(Bounds.Left());
-	bbox[BOXTOP] = GetBlockY(Bounds.Top());
-	bbox[BOXBOTTOM] = GetBlockY(Bounds.Bottom());
+	bbox[BOXRIGHT] = level.blockmap.GetBlockX(Bounds.Right());
+	bbox[BOXLEFT] = level.blockmap.GetBlockX(Bounds.Left());
+	bbox[BOXTOP] = level.blockmap.GetBlockY(Bounds.Top());
+	bbox[BOXBOTTOM] = level.blockmap.GetBlockY(Bounds.Bottom());
 	// add the polyobj to each blockmap section
 	for(int j = bbox[BOXBOTTOM]*bmapwidth; j <= bbox[BOXTOP]*bmapwidth;
 		j += bmapwidth)
@@ -1398,6 +1402,8 @@ void FPolyObj::ClosestPoint(const DVector2 &fpos, DVector2 &out, side_t **side)
 static void InitBlockMap (void)
 {
 	int i;
+	int bmapwidth = level.blockmap.bmapwidth;
+	int bmapheight = level.blockmap.bmapheight;
 
 	PolyBlockMap = new polyblock_t *[bmapwidth*bmapheight];
 	memset (PolyBlockMap, 0, bmapwidth*bmapheight*sizeof(polyblock_t *));
diff --git a/src/portal.cpp b/src/portal.cpp
index 15d012416c..1ec92799f4 100644
--- a/src/portal.cpp
+++ b/src/portal.cpp
@@ -113,14 +113,16 @@ struct FPortalBits
 
 static void BuildBlockmap()
 {
+	auto bmapwidth = level.blockmap.bmapwidth;
+	auto bmapheight = level.blockmap.bmapheight;
+
 	PortalBlockmap.Clear();
 	PortalBlockmap.Create(bmapwidth, bmapheight);
 	for (int y = 0; y < bmapheight; y++)
 	{
 		for (int x = 0; x < bmapwidth; x++)
 		{
-			int offset = y*bmapwidth + x;
-			int *list = blockmaplump + *(blockmap + offset) + 1;
+			int *list = level.blockmap.GetLines(x, y);
 			FPortalBlock &block = PortalBlockmap(x, y);
 
 			while (*list != -1)
@@ -165,7 +167,7 @@ static void BuildBlockmap()
 
 void FLinePortalTraverse::AddLineIntercepts(int bx, int by)
 {
-	if (by < 0 || by >= bmapheight || bx < 0 || bx >= bmapwidth) return;
+	if (by < 0 || by >= PortalBlockmap.dx || bx < 0 || bx >= PortalBlockmap.dy) return;
 
 	FPortalBlock &block = PortalBlockmap(bx, by);
 
@@ -743,9 +745,9 @@ DVector2 P_GetOffsetPosition(double x, double y, double dx, double dy)
 		// Try some easily discoverable early-out first. If we know that the trace cannot possibly find a portal, this saves us from calling the traverser completely for vast parts of the map.
 		if (dx < 128 && dy < 128)
 		{
-			int blockx = GetBlockX(actx);
-			int blocky = GetBlockY(acty);
-			if (blockx < 0 || blocky < 0 || blockx >= bmapwidth || blocky >= bmapheight || !PortalBlockmap(blockx, blocky).neighborContainsLines) return dest;
+			int blockx = level.blockmap.GetBlockX(actx);
+			int blocky = level.blockmap.GetBlockY(acty);
+			if (blockx < 0 || blocky < 0 || blockx >= PortalBlockmap.dx || blocky >= PortalBlockmap.dy || !PortalBlockmap(blockx, blocky).neighborContainsLines) return dest;
 		}
 
 		bool repeat;