Tags: Cave.
Sơn Đoòng cave (hang Sơn Đoòng Mountain River cave in Vietnamese) is a cave in Phong Nha-Kẻ Bàng National Park Bố Trạch District Quảng Bình Province Vietnam. As of 2009 it is the biggest known cave in the world and is located near the Laos–Vietnam border (17°27’25.88N 106°17’15.36E). Inside is a large fast-flowing underground river.