A cave expedition member works in a cave connecting Jiayang Tiankeng (an area of naturally formed pits) in Napo County, south China's Guangxi Zhuang Autonomous Region on Nov 3, 2019. [Photo/Xinhua]

A cave expedition member stands among trees at the bottom of Nongyang Tiankeng (an area of naturally formed pits) in Napo County, south China's Guangxi Zhuang Autonomous Region on Nov 2, 2019. [Photo/Xinhua]