Minecraft wiki entry for Exploring_an_ancient_city, associated text: There is a Redstone lab under the city centre of the Ancient City. You can find the city center easily because it contains a statue that looks like a Warden face. The secret door to the lab can only be opened through a specific method, which is random each time. First, you must find the chest in front of the “Warden face” and open it. Then grab the Golden Carrot inside the chest and go down to the bridge opposite to the chest (don’t eat the carrot yet). Finally, go under the center and you will see two recessed Deepslate walls; these are the doors. To open the door, go to the door that has a Chiseled Deepslate block on it and eat the Golden Carrot. This will activate the Sculk sensor behind the door and open it. If there is a golden apple, then eat it while on the tiled deepslate to open the door. When there is two walls, walk between them to open the door. If there's nothing, then walk on tiles to the left of the door where you would normally find the chest to open it. At the moment, the lab does not contain any noteworthy loot, apart a lot of Redstone blocks, which are not particularly rare, but it has educational purpose for new players, as it teaches them about how Sculk sensors can be used for wireless Redstone. It could also be a secret base after you remove the stuff inside and fully secure the Ancient City.