Son Doong Cave

Discovered in 1991, Son Doong Cave in Quang Binh Province is 3 million years old, one of the widest caves in the world. Lying in National Park Phong Nha - Ke Bang, the mysterious underground world contains an underground river with a huge number of stalactites. The cave is open to the public from February to August. However, it only receives a fixed number of visitors.

The photo courtesy of VN Express