Karst ave is the passage of underground river. Cave is derived from groundwater dissolution through crevices in the rock. The 400m long Baiyun Cave is the largest cave of Naigu Stone Forest. Though not very large, Baiyun Cave displays fantastic underground world, containing rich speleothem including stalactite, stalagmite, rim stone, stone flower, etc. With stone forest above ground and cave underground, Naigu Stone Forest shows “vertical” karst.