A Perfectly Round
Tianxuan Tiankeng in Zhenba County, Hanzhong, has a nearly perfectly round opening. Its width reaches 110 meters and depth 150 meters. The tiankeng’s west wall is well preserved, almost vertical, while the east collapsed and was covered by Quaternary overlay. The collapsed rocks and earth formed a small mound at the tiankeng’s bottom and was covered by sparse shrubs, grass and moss.