Son Doong Cave.

Two seven day/six night tours will be held each month at a cost of US$ 3,000. Three five day/four night tours will be held each month for US$ 2,300. The tours begin in August 2013. 

Each tour accommodates six tourists and about 15 local guides. After the trial period, if operations go well, adventure tours in Son Doong Cave will operate officially from February to August every year. 

Son Doong cave, located in Phong Nha-Ke Bang National Park, was first discovered in 1991. Its existence was publicized in 2009 by a group of British scientists from BCRA, led by Howard Limbert, after their surveying trip in Phong Nha-Ke Bang Park. 

According to Limbert, the cave is five times larger than the nearby Phong Nha cave, previously considered to be the largest in Vietnam. 

Son Doong cave is found to have a length of at least 5 kilometres. It is estimated to be 200 metres in width and 150 metres in height.

Source: VietNamNet Bridge