Hang Sơn Đoòng

Hang Sơn Đoòng is the largest known cave in the world. It is located in the Phong Nha National Park in the North Central Region of Vietnam. The cave is hidden under dense jungle within rugged mountains, and was discovered in 1991 by a local man looking for rare timber.

Tourists visits to the cave are quite expensive, at around $3000 per person.why?

The cave is a UNESCO world heritage site and is very well protected. It is similar to the Sabang Underground River in Palawan.