This is the main entrance of Huyen Khong cave from the inside looking at the four guards on either side of the steps http://en.wikipedia.org/wiki/Marble_Mountains_%28Vietnam%29
The entrance to this spectacular chamber is guarded by two administrative mandarins (to the left of the doorway) and two military mandarins (to the right) Vietnam Lonely Planet. Nick Ray, Peter Dragicevich, Regis St. Louis Edition 9 publisher=Lonely Planet date=2007 ISBN=1741043069