This photo released yesterday shows an inside look of one of two giant karst sinkholes discovered by a cave exploration team after its one-week-long adventure in Donglan, South China’s Guangxi, between Nov. 24 and 30. Giant sinkholes, also known as “Tiankeng” in Chinese, are dolines, or giant pits, with special geological features found in karst regions formed by repeated cave-ins. They are mainly found in China, Mexico and Papua New Guinea. Xinhua