A view of a tiankeng in Wude town, Zhenxiong county, Southwest China’s Yunnan province, July 8, 2015. "Tiankeng", a Chinese term that literally means "heavenly pit", refers to a unique geological feature - karst doline. The name was proposed by a senior Chinese geologist as there was no special term to define the natural wonder, which are formed by repeat cave-ins and are usually over 100 meters both in depth and diameter. The six tiankengs in Zhenxiong cover an area of 40 hectares, and 32 people from eight families live in the largest one, Daguoquan (big pan edge). The earliest villagers started living there in 1953 and are basically self-sufficient. Now the government has laid a new road connecting the primitive village to the outside world. Experts from the China Geological Survey said in June the tiankeng cluster in Xiongxian is the largest in Yunnan province. (Photo: China News Service/Zhang Guangyu)
