The Hammerboy's Cavern is a dark and damp underground room. It is discovered when Klaymen enters the small brown house from the lower section of the desert. After he enters a brown room, he immediately falls into a hole in the floor. He manages to hold himself on the edges from falling in, but the Hammerboy comes in with a hammer and knocks Klaymen into the hole.
The room contains a disk and a teleport machine, which is the only way out. There are three glowing symbols on the wall, which are to be input into the cannon in order to enable moving it horizontally.