Son Doong, the world’s largest known cave by volume, is in Vietnam.
The cave lies in Phong Nha-Ke Bang National Park in Quang Binh Province. Local resident Ho Khanh first found the entrance in 1990, but British cavers explored and surveyed it systematically in 2009. The cave’s Vietnamese name means “Mountain River Cave,” referring to the underground river that runs through it.
Son Doong is famous for its enormous chambers, jungle-filled collapse dolines, and unusual cave weather. Its main passage is more than 5 kilometres long in surveyed sections, and some chambers are tall enough to contain a large skyscraper. It is often confused with Deer Cave in Malaysia, another very large Asian cave, but Son Doong is the one most commonly described as the world’s largest by volume.
Phong Nha-Ke Bang also contains many other extensive caves and became a UNESCO World Heritage Site in 2003.