Forty-nine vast sinkholes have been discovered in the mountains in Hanzhong city of northwest China’s Shaanxi Province. The discoveries were made during a survey conducted over the past four months. Sinkholes are a type of natural cave with a diameter and depth of over 100 meters.
They contain one or more significant vertical shafts, rather than being conventional horizontal caves. Sinkholes typically form in limestone landscapes as a result of long-term erosion by water. Most can only be negotiated safely with the use of ropes or ladders.