Son Doong Cave is located in the heart of the Phong Nha Ke Bang National Park in Quang Binh province of Central Vietnam. Only recently explored in 2009-2010 by the British Cave Research Association, Son Doong Cave has only been open to the public since 2013. All research and tourist expeditions have thus far have been organized and led by local adventure tour company Oxalis, in partnership with British Cave Research Association and with the permission of the government of Vietnam.
Source: Oxalisadventure.com