At more than 200 meters high, 150 meters wide and 5 kilometers long, the Hang Son Doong Cave in Vietnam is so big that it has its own jungle, river and climate. The cave is quite a humbling and belittling experience to visitors. It’s huge and it looks like it was taken from Tolkien’s Lord of the Rings! The cave was created two to five million years ago by river water eroding the limestone underneath a mountain. It was first discovered in 1991 by a local farmer and is now among the most amazing places to visit in Asia.