(VOV) - Thien Duong cave in Phong Nha-Ke Bang national park in the central province of Quang Binh has been considered as the longest in the world.
From a 5km stretch of the cave discovered in 2005, the British Cave Research Association continued in 2010 that it was 31.4km long.
The cave has been open to the public and visitors have to climb 524 steps to reach the cave.
Inside there is a 1km long and 1m wide wooden bridge, the longest of its kind ever seen in Vietnam.