Thien Duong, a cave with a length
of 31 km which was discovered only in 2005 by scientists of the
British Caving Research Association, is the longest dry cave in
the world. The 980 meter long Tien Son Cave, depicted
here, is located at an altitude of ca. 200 meter,
up the cliff from Phong Nha Cave (fig.)
and is accessible by a stairway that starts from the Son River (fig.) below.