The world’s largest natural caveHang Son Đoòng holds the Guinness World Records title for the largest natural cave in the world – specifically, for being the largest single cave passage. The mist in Hang Son Đoòng creates the illusion of clouds within the cave system - Geng Xu/Getty ImagesHang Son Đoòng ecologyA large underground river system flows through Hang Son Đoòng, creating a special ecosystem within the cave. A stream, Rao Thuong, flows through the cave and this is where Hang Son Đoòng gets its name from. Cavers have seen flying squirrels and snakes within Hang Son Đoòng, and the odd monkey descends into the cave to forage. In the wider cave system, more than seven new species have been discovered, including frogs, fish, scorpions and cave swiftlets.