Introduction to the Karst Cave Group: The Wulongshan Karst Cave Group is mainly distributed on both sides of the Grand Canyon. There are 212 large and small caves discovered so far, with different causes and different landscapes, forming a strange underground world. Among them, Wulong Cave was formed 600,000 to 700,000 years ago. The fossilized leg bones and teeth of ancient vertebrates that lived here 300,000 to 400,000 years ago have been found in the cave.