Boulder Nightmare is an Advanced difficulty map. The map takes place in a large collection of rock formations, with heavy haze noticeable on the map for much of the time. The Bloons will spawn alternating between the left and right sides of the central rock formation, and cannot be hit while underneath the formations on the track. MOAB-Class Bloons will fly over the small formations and will not gain such immunity. The rock formations cannot be built upon, although the gray piles in the corners of the map are destructible.