diff --git a/common/src/main/java/com/cursedcauldron/wildbackport/common/tag/WBBiomeTags.java b/common/src/main/java/com/cursedcauldron/wildbackport/common/tag/WBBiomeTags.java
index ddf81c9..bc07603 100644
--- a/common/src/main/java/com/cursedcauldron/wildbackport/common/tag/WBBiomeTags.java
+++ b/common/src/main/java/com/cursedcauldron/wildbackport/common/tag/WBBiomeTags.java
@@ -12,4 +12,5 @@ public class WBBiomeTags {
     public static final TagKey<Biome> SPAWNS_WARM_VARIANT_FROGS = TAGS.create("spawns_warm_variant_frogs");
     public static final TagKey<Biome> SPAWNS_COLD_VARIANT_FROGS = TAGS.create("spawns_cold_variant_frogs");
     public static final TagKey<Biome> ALLOWS_SURFACE_SLIME_SPAWNS = TAGS.create("allows_surface_slime_spawns");
+    public static final TagKey<Biome> HAS_ANCIENT_CITY = TAGS.create("has_structure/ancient_city");
 }
\ No newline at end of file
diff --git a/common/src/main/resources/data/minecraft/tags/worldgen/biome/has_structure/ancient_city.json b/common/src/main/resources/data/minecraft/tags/worldgen/biome/has_structure/ancient_city.json
new file mode 100644
index 0000000..2e42949
--- /dev/null
+++ b/common/src/main/resources/data/minecraft/tags/worldgen/biome/has_structure/ancient_city.json
@@ -0,0 +1,6 @@
+{
+    "replace": false,
+    "values": [
+      "minecraft:deep_dark"
+    ]
+}
\ No newline at end of file