Images trouvées ci et là sur internet. Je n’en ai pas toujours la provenance ni l’auteur. Qu’ils ou elles me pardonnent si j’utilise ces images sans leur accord.

Er Wang Dong, « la seconde caverne royale » (Chine)

Vu ici et

Er Wang Dong (二王洞; literally: « Second Royal Cave ») is a large cave in the Wulong Karst region, in Wulong County of Chongqing Municipality of China.
Current known length of its passages is 42,139 metres (138,251 ft) with a maximum depth of 441 m (1,447 ft). It is large enough to contain its own weather system. The cave starts in the 195 m (640 ft) deep Niubizi tiankeng (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.
Both caves were explored by Hong Meigui Cave Exploration Society. Local people make weather forecast based on the observations in Niubizi tiankeng – if there is a fog coming from the cave, rain is expected. (from Wiki En)