Caves Terrain is a special, but unmarked terrain in Bloons Monkey City (similar to Volcano Terrain). There are five cave terrain tiles on every map and it is believed this could be linked to a Portal Artifact. Gameplay is the same as normal. This type of terrain favors Ice Monkeys but restricts Monkey Aces, Banana Farms, Dartling Guns and Heli Pilots, unless when played in Replay Tracks on Flash. On Flash's Replay Tracks, Monkey Engineers are favored while Monkey Aces and Mortar Monkeys are restricted.