You read that right, a group of adventurers discovered a cave system so massive that it even has its own weather system, complete with wispy clouds and lingering fog. Expert cavers have explored some of the vast caverns in the Chongquing province of China and have taken the first-ever photographs of the natural wonder. Continue reading for a video, more pictures and information.

According to photographer and caver Robbie Shone, “A few of the caves had previously been used by nitrate miners, at the areas close to the entrance, but had never been properly explored before. All the major passageways were deep underground and had never seen light before.”