Er Wang Dong Cave, Wulong Karst, Wulong County, Chongqing Municipality, China

The length of the cave has been variously estimated as 3,000 metres (9,800 ft), 8,297 metres (27,221 ft), or 26,021 metres (85,371 ft). It is large enough to contain its own weather system.
Cloud Ladder Hall, one of the chambers inside which measures about 5 hectares (12 acres), is large enough that a layer of fog conceals the roof 250 metres (820 ft) above. "I had never seen anything quite like the inside cloud ladder before," said Manchester photographer and caver Robbie Shone, one of a team of 15 explorers on a month-long expedition who first photographed the cave in September 2013. "Thick cloud and fogs hangs in the upper half of the cave, where it gets trapped and unable to escape through the small passage in the roof."