One of the largest caves in the world, and certainly the largest in Vietnam, is Hang Son Doong. Approximately three million years old, Hang Son Doong Cave is an incredible destination unlike anywhere else on the planet. The cave is enormous, and it is possible for dozens of people to camp within it at a time. Bright blue water pools are located in the cave, and a river runs through it.
Formed on the edge of a fault zone, Hang Son Doong has been carved out by the mighty Rao Thuong River as it erodes away the limestone, forming the enormous tunnel beneath the Annamite Mountains. Giant sinkholes, known as dolines, have collapsed sometime up to 300’000 years ago, creating massive openings to the outside world.