Introduction to the Yanzi Tiankeng: The Yanzi Tiankeng is located in the hinterland of the Dashiwei Tiankeng Group. Its mouth has a maximum diameter of 100 meters, a maximum depth of 250 meters, and an average depth of 171 meters. It is a medium-sized tiankeng with a small mouth and a large interior. Because it is shaped like a bucket and is surrounded by cliffs, explorers can only rely on a 140-meter static rope from the bottom of the pit entrance and use SRT single rope technology to explore the Yanzi sinkhole.