Xiaozhai Tiankeng is what geologists call a sinkhole or ditch, a depression of the land generated, among other factors, by the effect of water. In this case, it was formed on top of a cave and houses an underground river measuring a total of 8.5 kilometers and flows into a spectacular waterfall. Its enormous size makes it the sinkhole of its kind, known as tiankeng, the largest and deepest in the world. #Nature
