Located just 500 meters from Tham Lot, the cave can only be visited by boat from Bo Tho Pier. The cave is in Phi Hua To Mountain which is surrounded by mangrove swamps. There are 2 different paths inside the cave. On the left lies the shortcut to the back of the cave where the sunlight can shine through, and on the right is a path to a natural hall believed to have been a shelter for prehistoric people. Prehistoric paintings of men, animals, human organs and numerous seashells can be seen in the cave. The discovery of big human skulls in the cave, resulted in the caves present name.