diff --git a/README.md b/README.md
index efba26d..80422b3 100644
--- a/README.md
+++ b/README.md
@@ -64,6 +64,7 @@ Useful options:
 - `--sea-level L`: sea level, default `70`.
 - `--snow-line H`: snow threshold, default `sea-level + 38`.
 - `--trails`: enable trail and cabin prepass.
+- `--wall`: build a brutalist border wall around the generated area.
 - `--format mca|bin`: write Minecraft region files or raw debug chunks.
 - `--out DIR`: output directory.
 
diff --git a/worldgen-c/bin/worldgen b/worldgen-c/bin/worldgen
index 20868a8..1815d62 100755
Binary files a/worldgen-c/bin/worldgen and b/worldgen-c/bin/worldgen differ
diff --git a/worldgen-c/include/worldgen.h b/worldgen-c/include/worldgen.h
index b47f549..4ba75c2 100644
--- a/worldgen-c/include/worldgen.h
+++ b/worldgen-c/include/worldgen.h
@@ -53,7 +53,11 @@
 		BLOCK_LADDER_N = 40,
 		BLOCK_LADDER_S = 41,
 		BLOCK_LADDER_W = 42,
-		BLOCK_LADDER_E = 43
+		BLOCK_LADDER_E = 43,
+		BLOCK_SMOOTH_STONE = 44,
+		BLOCK_STONE_BRICKS = 45,
+		BLOCK_BLACKSTONE = 46,
+		BLOCK_IRON_BARS = 47
 	};
 
 struct trail_segment;
diff --git a/worldgen-c/src/main.c b/worldgen-c/src/main.c
index 8e294e5..e27a2a5 100644
--- a/worldgen-c/src/main.c
+++ b/worldgen-c/src/main.c
@@ -144,7 +144,11 @@ static const block_state BLOCK_STATE_TABLE[] = {
 	[BLOCK_LADDER_N] = {"minecraft:ladder", PROPS_LADDER_N, 2},
 	[BLOCK_LADDER_S] = {"minecraft:ladder", PROPS_LADDER_S, 2},
 	[BLOCK_LADDER_W] = {"minecraft:ladder", PROPS_LADDER_W, 2},
-	[BLOCK_LADDER_E] = {"minecraft:ladder", PROPS_LADDER_E, 2}
+	[BLOCK_LADDER_E] = {"minecraft:ladder", PROPS_LADDER_E, 2},
+	[BLOCK_SMOOTH_STONE] = {"minecraft:smooth_stone", NULL, 0},
+	[BLOCK_STONE_BRICKS] = {"minecraft:stone_bricks", NULL, 0},
+	[BLOCK_BLACKSTONE] = {"minecraft:blackstone", NULL, 0},
+	[BLOCK_IRON_BARS] = {"minecraft:iron_bars", NULL, 0}
 };
 
 static const block_state *get_block_state(uint16_t id) {
diff --git a/worldgen-c/src/worldgen.c b/worldgen-c/src/worldgen.c
index 53c0f93..48b9d90 100644
--- a/worldgen-c/src/worldgen.c
+++ b/worldgen-c/src/worldgen.c
@@ -3558,7 +3558,12 @@ static void generate_chunk_border_wall(worldgen_ctx *ctx, int chunk_x, int chunk
 	if (!ctx->enable_wall) return;
 	if (ctx->wall_min_x > ctx->wall_max_x || ctx->wall_min_z > ctx->wall_max_z) return;
 
-	const int wall_height = 9;
+	const int wall_depth = 4;
+	const int wall_height = 18;
+	const int tower_depth = 9;
+	const int tower_height = 28;
+	const int tower_spacing = 32;
+	const int tower_half_width = 4;
 	for (int dx = 0; dx < CHUNK_SIZE; ++dx) {
 		for (int dz = 0; dz < CHUNK_SIZE; ++dz) {
 			int world_x = chunk_x * CHUNK_SIZE + dx;
@@ -3566,9 +3571,34 @@ static void generate_chunk_border_wall(worldgen_ctx *ctx, int chunk_x, int chunk
 			if (world_x < ctx->wall_min_x || world_x > ctx->wall_max_x) continue;
 			if (world_z < ctx->wall_min_z || world_z > ctx->wall_max_z) continue;
 
-			int on_border = world_x == ctx->wall_min_x || world_x == ctx->wall_max_x ||
-			                world_z == ctx->wall_min_z || world_z == ctx->wall_max_z;
-			if (!on_border) continue;
+			int dist_min_x = world_x - ctx->wall_min_x;
+			int dist_max_x = ctx->wall_max_x - world_x;
+			int dist_min_z = world_z - ctx->wall_min_z;
+			int dist_max_z = ctx->wall_max_z - world_z;
+			int side_dist = dist_min_x;
+			int along = world_z;
+			if (dist_max_x < side_dist) {
+				side_dist = dist_max_x;
+				along = world_z;
+			}
+			if (dist_min_z < side_dist) {
+				side_dist = dist_min_z;
+				along = world_x;
+			}
+			if (dist_max_z < side_dist) {
+				side_dist = dist_max_z;
+				along = world_x;
+			}
+
+			int phase = along % tower_spacing;
+			if (phase < 0) phase += tower_spacing;
+			int tower_offset = phase;
+			if (tower_offset > tower_spacing / 2) tower_offset = tower_spacing - tower_offset;
+			int near_corner = (dist_min_x < tower_depth || dist_max_x < tower_depth) &&
+			                  (dist_min_z < tower_depth || dist_max_z < tower_depth);
+			int in_tower = side_dist < tower_depth && (tower_offset <= tower_half_width || near_corner);
+			int in_wall = side_dist < wall_depth || in_tower;
+			if (!in_wall) continue;
 
 			column_data data = get_column_data(ctx, world_x, world_z);
 			int visible_base = data.height;
@@ -3577,7 +3607,8 @@ static void generate_chunk_border_wall(worldgen_ctx *ctx, int chunk_x, int chunk
 			}
 			if (visible_base >= CHUNK_HEIGHT - 1) continue;
 
-			int top = visible_base + wall_height;
+			int height = in_tower ? tower_height : wall_height;
+			int top = visible_base + height;
 			if (top >= CHUNK_HEIGHT) top = CHUNK_HEIGHT - 1;
 
 			for (int y = data.height + 1; y < CHUNK_HEIGHT; ++y) {
@@ -3585,12 +3616,28 @@ static void generate_chunk_border_wall(worldgen_ctx *ctx, int chunk_x, int chunk
 			}
 			out->heightmap[dx][dz] = (uint16_t)data.height;
 
-			int start = data.height + 1;
+			int start = data.height - 3;
 			if (start < 1) start = 1;
 			for (int y = start; y <= top; ++y) {
-				uint16_t block = (y == top) ? BLOCK_OAK_PLANKS : BLOCK_STONE;
+				int rel_y = y - visible_base;
+				uint16_t block = BLOCK_SMOOTH_STONE;
+				if (rel_y <= 2 || rel_y % 6 == 0 || rel_y == height - 1) {
+					block = BLOCK_STONE_BRICKS;
+				}
+				if (in_tower && side_dist == 0 && rel_y >= 9 && rel_y <= 17 &&
+				    (tower_offset == 0 || (rel_y == 13 && tower_offset <= 3))) {
+					block = BLOCK_BLACKSTONE;
+				} else if (in_tower && side_dist == 1 && tower_offset == 0 && rel_y >= 4 && rel_y <= 7) {
+					block = BLOCK_IRON_BARS;
+				} else if (!in_tower && side_dist == 0 && rel_y >= 7 && rel_y <= 10 && phase % 16 == 8) {
+					block = BLOCK_IRON_BARS;
+				}
 				set_block_with_height(out, dx, dz, y, block);
 			}
+			if (top + 1 < CHUNK_HEIGHT && (side_dist == 0 || side_dist == wall_depth - 1 || in_tower) &&
+			    phase % 4 < 2) {
+				set_block_with_height(out, dx, dz, top + 1, BLOCK_STONE_BRICKS);
+			}
 		}
 	}
 }