Ancient City Underground
by xkk-112358
Ancient City Underground changes how Ancient Cities generate, placing them more densely in underground Overworld biomes on Fabric servers.
What it does
The Fabric mod reworks Ancient City generation so cities appear in underground Overworld biomes, a range that vanilla restricts to the Deep Dark. Cities are spaced 10 chunks apart, and a 128-block city radius lets the structures cover each chunk with moderate overlap, without heavy clustering.
When a player joins for the first time, the game places them somewhere open inside the closest city, such as a walkway or courtyard. A bedrock layer at Y=60 closes off the underground world, so mobs cannot generate above it. The mod is server-side only, so only the server needs it, and single-player worlds run it as normal. Fabric Loader 0.19.3 is required. The code is open source under the CC0 1.0 Universal license, and the source code and issue tracker are public.
Vanilla End Portals, Strongholds and other structures are unaffected, so the mod coexists with them. Files exist for Fabric only, for game version 1.21.11, with 1.0.0 as the latest file from 2026-07-15.
Key features
Dense underground cities
Ancient Cities generate across underground Overworld biomes, not only inside the Deep Dark.
Chunk-covering layout
Cities spaced 10 chunks apart with a 128-block radius cover the map with moderate overlap.
Safe player spawning
New players join in an open area of the nearest city rather than in a hostile location.
Bedrock roof
A bedrock layer at Y=60 closes off the underground, and mobs do not generate above it.
Gallery
Compatibility
Latest build for each game version and loader.
Only full game releases are shown. This mod publishes no snapshot builds.
Use cases
Who it’s for: Server owners and players who want Ancient Cities to be a regular part of underground exploration in Overworld biomes.
How it compares
Deep Dark Expanded is open source under the MIT License and runs on both client and server, with files for 1.21.11, so every player needs it too. ChunkMix is under a Creative Commons Attribution Non Commercial No Derivatives 4.0 license and publishes files for 1.21.1 only; the client needs it, while the server can run without it. Underground Dimension runs on Fabric, Forge, NeoForge and Quilt for 1.21 – 1.21.5, and is not open source; the server needs it, while clients can leave it out.
| Mod | Loaders | Game versions | Environment | Updated |
|---|---|---|---|---|
| Ancient City Underground | Fabric | 1.21.11 | Server-side only | 2026-07-15 |
| Deep Dark Expanded | Fabric | 1.21.11 | Client and server | 2026-01-14 |
| ChunkMix | Fabric | 1.21.1 | Client required, server optional | 2026-04-29 |
| Underground Dimension | Fabric, Forge, NeoForge and Quilt | 1.21 – 1.21.5 | Server required, client optional | 2025-05-31 |
Questions
Does Ancient City Underground need Fabric API?
Do clients need to install the mod?
Does the mod work in single-player?
Which game versions does the mod support?
In the catalog
Ancient City Underground is one of 8,515 World generation mods on ModsFinder, and one of 4,027 World generation mods for Fabric. 19,862 mods support Minecraft 1.21.11.
Similar mods
What the author says
This is a SERVER-SIDE mod. It works on dedicated servers, and clients do not need to install it. For single-player, it works as normal.
Official listing
- Modrinth page
- modrinth.com/mod/ancient-city-underground
- Owner
- xkk-112358
- Published
- 2026-07-15
- Updated on Modrinth
- 2026-07-15
- Facts verified
- 2026-10-15