Son Doong Cave

Son Doong Cave lies in Phong Nha-Ke Bang National Park in Quang Binh province, Vietnam, near the border with Laos, formed as a solutional cave in Carboniferous and Permian limestone. It holds the world's largest known cave passage by volume: the main passage runs more than 5 kilometers long, 200 meters high and 150 meters wide, a cross-section believed to be twice that of the next largest known passage, in Deer Cave, Malaysia, with the wider system extending about 9 kilometers. The cave is estimated to be between two and five million years old, and hosts some of the tallest known stalagmites in the world, up to 80 meters tall, alongside an underground river. A local resident, Ho Khanh, found the entrance in 1990 while searching for agarwood, but the cave was not formally surveyed until the British Cave Research Association mapped it in April 2009, measuring its volume at roughly 38.5 million cubic meters, with a further expedition in 2010 exploring the passage in full. This entity documents Son Doong Cave specifically as a geological formation, a solutional limestone cave holding the world's largest cave passage.