Ancient cities generate deep underground in the deep dark, and they hold the only naturally occurring Swift Sneak books plus some of the best loot in the game. The map shows where they are, so you can dig straight down near one instead of tunnelling on hope.

• Bring wool. The Warden hears you, and sculk sensors are the whole defence mechanism of the city.
• Ancient cities sit far below sea level in the deep dark biome — the surface directly above one usually gives no hint at all.