Phong Nha-Ke Bang / Son Doong Cave

Son Doong Cave Expedition

Son Doong, said to be the world's largest cave passage, can only be visited on the officially permitted multi-day expedition run by Oxalis Adventure in partnership with the national park: six days of jungle trekking, river crossings and camping inside enormous chambers with their own forest. It is a challenging trip with limited places and fitness requirements, so book far ahead through the operator.