On the outside, a Mant Hill entrance resembles a large nest with a hole in the center where the player can enter. On the inside, the Mant Hill consists of a series of tunnels that go from room to room, similar to the Ancient Pig Ruins. Each Mant Hill is connected to the two others via the underground rooms, but none of them leads to another island.
The various rooms may contain Lamps, Honey Chests, Stalagmites or Antcomb Homes (where the Mants spawn as larvae). All of these structures can be hammered or mined, though they are not renewable. Mants will not become aggressive upon mining/hammering these structures. The Queen Womant Den entrance is also to be found in here.
When being inside Mant Hills, there is no loss of Sanity in darkness.
Each room has 4 walls. On each of these 4 walls there may, or may not be a Door, leading to another similar room. If two rooms are interconnected, the World Map will signal this by a two-way arrow (notice that the Map will only reveal rooms that have already been visited).
Periodically, earthquake-like rumbling will occur, causing many passageways in the Mant Hill to change place, including those in the room the player is standing in. After an earthquake, passageways signaling two previously interconnected rooms will display a "?" instead of the two-ways arrow, signaling that it may have changed. If that room is re-entered, the "?" will either change back into an arrow, or disappear. The exits, however, will never change position and the player will never be unable to reach one.
- Trying to spawn a Mant hill manually with the console command will crash the game. The bug reporting window will state: "THIS ROOM ALREADY EXISTS".