Son Doong cave (Vietnamese : Hang son Doong) is world's largest cave, located in Quang Binh province, Vietnam. It was 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 2-5 million years ago by river water eroding away the limestone underneath the mountain. Where the limestone was weak, the ceiling collapsed creating huge skylights.

The cave has only been open to the public since 2013. Jungles emerge from inside the cave itself, a scene so surreal that you have to see it to believe it. Misty clouds envelop the whole scene, a result of the cave’s own localized weather system.

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 meters, this comfortably surpasses Deer Cave in Malaysia, which was considered to be the previous record holder. It's over 5.5 miles long, has a jungle and river, scientists have discovered never-before-seen plant species around Son Doong’s waterfalls. 

But nobody knew any of that until about six years ago.