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 (牛鼻子天坑; "ox nose sinkhole") 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.