Er Wang Dong (Chinese: 二王洞; lit.
'Second Royal Cave') is a large cave in the Wulong Karst region, in Wulong County of Chongqing Municipality of China.
The cave starts in the 195 m (640 ft) deep Niubizi tiankeng (牛鼻子天坑; "ox nose sinkhole") and also contains the 295 m (968 ft) 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.
Local people make weather forecasts based on the observations in Niubizi tiankeng - if there is a fog coming from the cave, rain is expected.