Ancient City

bedrock

An ancient city is a generated structure found in the Deep Dark, harboring loot chests containing items that cannot be found anywhere else. It is made up of long corridors with wool floors (to prevent vibrations), as well as some smaller ruins off to the side of the main corridors, which contain 1-2 loot chests. The city center features a large rectangular structure resembling a warden's head, which contains reinforced deepslate, which is unobtainable in Survival mode.

Structure
The city features a massive palace-like structure that stretches throughout the biome. Unique blocks (such as reinforced deepslate) as well as different forms of deepslate can be found here. The loot in the chests includes several useful items for exploring the ancient city, such as snowballs and the Swift Sneak enchantment.

File structure
All ancient city structures found below are located in the folder client.jar/data/minecraft/structures/ancient_city.

Blocks
An ancient city is the only place in the Overworld where soul sand, soul soil, and polished basalt can generate naturally. It is also the only place in the game where a skeleton skull can generate naturally.

Issues
Issues pertaining to ancient cities get closed as "Invalid" on the bug tracker, as they are currently available only in experimental snapshots.

Concept artwork
Some concept art in this gallery was originally made for the Caves & Cliffs update.

Trivia

 * The city center of the ancient cities bears a striking resemblance to early iterations of the warden's design.