Son Doong Cave which is Mountain River cave in Vietnamese is a cave located in Phong Nha-Kẻ Bàng National Park, Bố Trạch District, Quảng Bình Province, Vietnam. As per 2009, this is the biggest known cave in the world and is located near the border of Laos and Vietnam. The cave is formed in Permian limestone and Carboniferous. There is a fast flowing underground river inside the cave. The cave is known to be five times larger than the cave of Phong Nha cave which was previously considered to be the biggest cave in Vietnam.
The biggest chamber of Son Doong is nearly five kilometres long with height of 200 metres and width of 150 metres. This cave is known to contain some of the tallest known stalagmites in the whole world and are up to nearly 70 m tall. In the early August 2013, the first tourist group explored the cave on a special guided tour at the cost of US$3,000 each. The good news is that future exploration are being planned for visiting this exclusive cave.
