diff --git a/worldgen-c/bin/worldgen b/worldgen-c/bin/worldgen
index 0ee30a5..91c42f2 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 11ac933..dbe1dc9 100644
--- a/worldgen-c/include/worldgen.h
+++ b/worldgen-c/include/worldgen.h
@@ -69,7 +69,9 @@
 		BLOCK_LILY_OF_THE_VALLEY = 56,
 		BLOCK_FERN = 57,
 		BLOCK_CLAY = 58,
-		BLOCK_SEAGRASS = 59
+		BLOCK_SEAGRASS = 59,
+		BLOCK_IRON_BARS_NS = 60,
+		BLOCK_IRON_BARS_EW = 61
 	};
 
 struct trail_segment;
diff --git a/worldgen-c/src/main.c b/worldgen-c/src/main.c
index b11f51e..bcbfe00 100644
--- a/worldgen-c/src/main.c
+++ b/worldgen-c/src/main.c
@@ -100,6 +100,8 @@ static const kv_pair PROPS_LADDER_N[] = {{"facing", "north"}, {"waterlogged", "f
 static const kv_pair PROPS_LADDER_S[] = {{"facing", "south"}, {"waterlogged", "false"}};
 static const kv_pair PROPS_LADDER_W[] = {{"facing", "west"}, {"waterlogged", "false"}};
 static const kv_pair PROPS_LADDER_E[] = {{"facing", "east"}, {"waterlogged", "false"}};
+static const kv_pair PROPS_IRON_BARS_NS[] = {{"east", "false"}, {"north", "true"}, {"south", "true"}, {"waterlogged", "false"}, {"west", "false"}};
+static const kv_pair PROPS_IRON_BARS_EW[] = {{"east", "true"}, {"north", "false"}, {"south", "false"}, {"waterlogged", "false"}, {"west", "true"}};
 static const size_t BLOCK_STATE_CAP = 256;
 static const int32_t DATA_VERSION = 2730; /* Java Edition 1.17.1; includes copper ore. */
 static const block_state BLOCK_STATE_TABLE[] = {
@@ -162,7 +164,9 @@ static const block_state BLOCK_STATE_TABLE[] = {
 	[BLOCK_LILY_OF_THE_VALLEY] = {"minecraft:lily_of_the_valley", NULL, 0},
 	[BLOCK_FERN] = {"minecraft:fern", NULL, 0},
 	[BLOCK_CLAY] = {"minecraft:clay", NULL, 0},
-	[BLOCK_SEAGRASS] = {"minecraft:seagrass", NULL, 0}
+	[BLOCK_SEAGRASS] = {"minecraft:seagrass", NULL, 0},
+	[BLOCK_IRON_BARS_NS] = {"minecraft:iron_bars", PROPS_IRON_BARS_NS, 5},
+	[BLOCK_IRON_BARS_EW] = {"minecraft:iron_bars", PROPS_IRON_BARS_EW, 5}
 };
 
 static const block_state *get_block_state(uint16_t id) {
@@ -353,6 +357,13 @@ static void pack_heightmap(const chunk_data *chunk, int64_t *out_longs, size_t o
 	}
 }
 
+static int column_contains_water(const chunk_data *chunk, int x, int z) {
+	for (int y = 1; y < CHUNK_HEIGHT; ++y) {
+		if (chunk->blocks[y][x][z] == BLOCK_WATER) return 1;
+	}
+	return 0;
+}
+
 static int section_has_blocks(const chunk_data *chunk, int section_y) {
 	int y_base = section_y * 16;
 	for (int y = 0; y < 16; ++y) {
@@ -444,7 +455,11 @@ static void write_section(buf *b, const chunk_data *chunk, int section_y) {
 
 static void build_chunk_nbt(const chunk_data *chunk, buf *out) {
 	int32_t biomes[256];
-	for (int i = 0; i < 256; ++i) biomes[i] = 1;  // Plains biome
+	for (int z = 0; z < CHUNK_SIZE; ++z) {
+		for (int x = 0; x < CHUNK_SIZE; ++x) {
+			biomes[z * CHUNK_SIZE + x] = column_contains_water(chunk, x, z) ? 0 : 1; // Ocean or plains
+		}
+	}
 
 	int64_t heightmap[37];
 	pack_heightmap(chunk, heightmap, 37);
diff --git a/worldgen-c/src/worldgen.c b/worldgen-c/src/worldgen.c
index 46376f6..2a179cc 100644
--- a/worldgen-c/src/worldgen.c
+++ b/worldgen-c/src/worldgen.c
@@ -3811,7 +3811,8 @@ static void generate_chunk_border_wall(worldgen_ctx *ctx, int chunk_x, int chunk
 			}
 			if (top + 1 < CHUNK_HEIGHT) {
 				if (!in_tower && (side_dist == wall_start || side_dist == wall_end)) {
-					set_block_with_height(out, dx, dz, top + 1, BLOCK_IRON_BARS);
+					uint16_t rail_block = (side < 2) ? BLOCK_IRON_BARS_NS : BLOCK_IRON_BARS_EW;
+					set_block_with_height(out, dx, dz, top + 1, rail_block);
 				} else if (in_tower && phase % 4 < 2) {
 					set_block_with_height(out, dx, dz, top + 1, BLOCK_STONE_BRICKS);
 				}