From the Super Mario Wiki
Belome Temple is located in the vast caverns underneath the desert of Land's End. It is unknown who built Belome Temple or why, all that is known is that the temple seems to honor the monster Belome. Shamans prowl the temple and will offer their service to anyone who has entered it, for a price of course. There is a large treasure room in the temple which is guarded by a large, golden and possibly sentient statue of Belome. The elevator in the temple seems to be enchanted and will either bring a traveler to the treasure room or will bring them to Belome himself. There is a pipe that is the only entrance to Monstro Town at the end of the temple. Lastly, the mysterious "Mokura" also wanders around the temple.