Hang Son Doong is world's largest cave, located in Quang Binh province, Vietnam.

It is found by a local man named Ho Khanh in 1991 and was recently discovered in 2009 by British cavers, led by Howard Limbert. The name "Son Doong" cave means "mountain river cave", It was created 3,5 million years ago by river water eroding away the limestone underneath the mountain Where the limestone was weak, the ceiling collapsed creating huge skylights..

At over 5km long, with sections reaching up to 200m tall and 150m wide, Hang Son Doong is large enough to house an entire New York City block, complete with 40 story skyscrapers. With a total measured volume of 38.5 million cubic metres, this comfortably surpasses Deer Cave in Malaysia, which was considered to be the previous record holder. Stalagmites up to 80m high have also been surveyed, the tallest ever encountered.

Less people have seen the inside of Hang Son Doong than have stood on the summit of Mount Everest...