Immortal Cave is an underground erosion sandstone cave from the Sinian period (0.57 - 0.8 billion years ago). The sandstone bedding is smooth with several high-angle joints and a small fault. Water flowing through cracks in the stone eroded the sandstone which eventually collapsed and formed the cave. Legend has it that Lu Dong Bin, one of the eight Taoist immortals, lived in seclusion and became immortal there. Ancient inscriptions from multiple dynasties can still be seen on the walls of the cave today.