Hang Sơn Đoòng, Mountain River Cave, Quang Binh Province, Vietnam

This amazing mammoth cave is situated in Vietnam. It is one of twenty such caves, which have jungles inside. Sometime the roof of the cave fell in, let sunlight in and all kinds of plants soon followed.
Son Doong cave (in Vietnamese: Hang Sơn Đoòng, meaning Mountain River Cave) is a cave in Phong Nha-Ke Bang National Park, Bo Trach District, Quang Binh Province, Vietnam. The cave is located near the Laos-Vietnam border. It has a large fast-flowing underground river inside.