<Tr> <Th> Length </Th> <Td> approx. 9 kilometres (5.6 mi) </Td> </Tr> <Tr> <Th> Discovery </Th> <Td> 1991 (AD) by Hồ Khanh </Td> </Tr> <Tr> <Th> Geology </Th> <Td> Permo - Carboniferous limestone </Td> </Tr> <Tr> <Th> Entrances </Th> <Td> </Td> </Tr>

The world's biggest cave hang son doong