<Tr> <Th> Hazards </Th> <Td> Underground river </Td> </Tr> <Tr> <Th> Cave survey </Th> <Td> 2009, British / Vietnamese </Td> </Tr> <P> Sơn Đoòng Cave (Vietnamese: Hang Sơn Đoòng ((haːŋ ˧ ʂəːn ˧ ɗɔ̤ŋ ˨ ˩));' cave of the mountain river' or' mountain cave of Đoòng (village)' in Vietnamese), is a solutional cave in Phong Nha - Kẻ Bàng National Park, Bố Trạch District, Quảng Bình Province, Vietnam . As of 2009 it has the largest known cave passage cross-section in the world, and is located near the Laos--Vietnam border . Inside is a large, fast - flowing subterranean river . It was formed in Carboniferous / Permian limestone and is believed to be between 2 and 5 million years old . </P> <P> Hang Sơn Đoòng was found by a local man named Hồ Khanh in 1991 . The whistling sound of wind and roar of a rushing stream in the cave heard through the entrance as well as the steep descent prevented the local people from entering the cave . Only in 2009 did the cave become internationally known after a group of cavers from the British Cave Research Association conducted a survey in Phong Nha - Kẻ Bàng from 10 to 14 April 2009 . Their progress was stopped by a large, 60 - metre (200 ft) high calcite wall, which was named the Great Wall of Vietnam . It was traversed in 2010 when the group reached the end of the cave passage . </P>

Where is the largest cave in the world located