Cross Son Doong, the world’s largest cave passage

What the experience is

Hang Son Doong lies in Phong Nha-Ke Bang National Park, in the limestone mountains of central Vietnam. By volume it is the largest cave passage known. The main passage is more than five kilometres long, and in places 200 metres high and 150 metres wide. In two places the roof collapsed long ago; light and rain enter, and forest has grown up on the rubble beneath, with trees thirty metres tall. Cloud can form inside the cave and drift along the passage.

The cave was surveyed only in 2009 and has been open to visitors since 2013, on one condition: they must walk and camp their way through it, in a guided expedition. One company, Oxalis Adventure, holds the licence. The expedition lasts six days and five nights in all. The group walks through jungle and across rivers, explores Hang En, itself one of the largest caves in the world, and camps in the forest near the entrance. The next two nights are spent inside Son Doong, beside each of the two openings. The exit is a climb of some ninety metres up a wall of flowstone, by ropes and ladders.

Who can do it

No caving experience is required, but the trip is demanding. It involves roughly 28 kilometres of jungle trekking and nine of caving, with many river crossings, scrambling over boulders and climbing on fixed ropes. The operator asks for evidence of a recent overnight trek and good fitness, and accepts guests aged 18 to 70. Each group of about ten is accompanied by a caving expert, guides, safety staff, cooks and porters. Access is tightly controlled by permit, so this is not a trip that can be arranged at short notice.

When to go

The season runs roughly from January to August; the cave is closed for the rest of the year, when the rivers flood. Departures are limited and book far in advance, so confirm availability with the operator.

Getting there

The base is the village of Phong Nha, reached from Dong Hoi, which has flights from Hanoi and Ho Chi Minh City and a station on the main north-south railway.

Why OKYTO recommends it

There are few places left where a traveller can be among the small number of people to have stood there. This is one, and it is run with care for the cave and for the people who carry the expedition. Our article Inside Son Doong has the full account. It pairs with a journey down the coast on The Vietage.