Er Wang Dong
Er Wang Dong is a large cave in the Wulong Karst region, in Wulong County of Chongqing Municipality of China.
Current known length of its passages is with a maximum depth of. It is large enough to contain its own weather system. The cave starts in the deep Niubizi tiankeng and also contains the deep Qingkou tiankeng.
Er Wang Dong cave has formed in Lower Ordovician limestone and is located close to another very large cave system - San Wang Dong.
Both caves were explored by Hong Meigui Cave Exploration Society. Local people make weather forecasts based on the observations in Niubizi tiankeng - if there is a fog coming from the cave, rain is expected.
