Sơn Đoòng Cave: Vietnam’s colossal underground world with its own weather
Vietnam’s Sơn Đoòng, discovered in the 1990s in Phong Nha-Kẻ Bàng National Park, is the world’s largest cave passage by volume, with a main route at least 6.5 km long and up to 200 m high and 150 m wide. Its vast interior can host a jungle, a river, and mist formed by natural cave ventilation after roof collapses, giving the impression of “own weather” while remaining connected to surface ecosystems. The site, formed over millions of years in a limestone karst landscape, is under environmental and heritage scrutiny as development pressures and conservation concerns surround the area.