Minecraft wiki entry for Desert_pyramid, associated text: In the center of the pyramid's 21×21 ground floor is a checkerboard pattern of terracotta and sandstone as a wind rose symbol, with a block of blue terracotta in the center. Underneath this terracotta is a secret room, the fosse, containing four chests, which are rigged by a stone pressure plate directly under the blue terracotta block. The pressure plate is connected to a 3×3 grid of TNT, which means that if a player or mob unintentionally steps on the plate, it sets off the nine TNT blocks, which destroy the chests and their loot.