Located near the Laos-Vietnam border, the Soon Doong cave is the largest cave in the world. This has a length of about 9km and its width and height are 200m and 150m respectively. It was first discovered by a local man named Ho Khanh and in 2009 Howard Limbert along with other British cavers explored it.
There is subterranean river, jungles and other cave ecosystems besides seventy meters tall stalagmite formations inside the cave. This is now open to visitors who are taken on guided tours against prior permission that is issued on a limited basis. via National Geographic | via Carsten Peter | via boredpanda