photo credits: Aidan Lyon
Located in Quang Binh province in the central part of Vietnam lies one of the world’s largest caves – so large that it has its own localised weather system. Despite being discovered by a local named Ho Khanh in 1991, this cave was only recently surveyed and explored by the British Cave Research Association in 2009. It is over 5km long and its largest cavern is over 200m tall and 150m wide – to give an idea of its size, a 747 could fly through its largest cavern.
Son Doong Cave, or Hang Son Doong meaning ‘Mountain River Cave’ is named after the river ‘Rao Thuong’ which runs through the cave system. The cave, although only partially cut-off from the outside jungle, has its own ecosystem and unique localised weather. Within the cave, explorers have found different species of birds, monkeys and snakes, as well as wild-life which were previously unknown to Vietnam, and it is believed there are still numerous species yet to be discovered thanks to the presence of ancient fossils that have adorned the passages for millions of years.
ACCESSING THE CAVES
Son Doong is located roughly in the centre of Vietnam along the border with Laos, situated within the Phong Nha-Ke Bang National Park, itself a UNESCO site note-worthy as the oldest karst system in Asia, having been formed around 400 million years ago.
A trip to see the cave system requires 4-5 days, trekking deep into the remote jungle of Phong Nha Ke Bang National Park, where you’ll cross river valleys and witness incredible cave formations along the way.
Situated roughly in central Vietnam near the Laotian border, the closest town to the cave is Dong Hoi, which can be reached by bus, train, or taxi. The journey begins with a two-hour trek down into the thick jungle and along a stream to arrive at Ban Doong village (pop. 40); all visitors must pass through here in order to reach Son Doong. This village is almost entirely cut off from the outside world and still practise a culture which has been relatively unchanged for hundreds of years.
From there, the hike continues for another two hours (6km) to the entrance of Hang En Cave – home to thousands of swiftlets – where a further 30-minute trek into the cavern will lead you to the first campsite. From here, the entrance to Son Doong Cave requires an 80m descent using ropes and safety lines.
EXPLORING SON DOONG’S DOLINES
The beginning of Son Doong starts with a river crossing, which is passable only when the water level is low, otherwise, it becomes impossible to make your way into the heart of the cave.
With millions of years to develop, the slow-dripping water from the Son Doong’s looming ceilings has formed large stalactites and stalagmites, making for a truly mesmerizing sight; the cave’s most notable stalagmite is the ‘Hand of Dog’ (named after its resemblance to a dog paw), quite possibly the world’s largest at 70m tall, found early on in the cave system in front of a large opening where light streams through.
A few hundred meters ahead will be your first campsite inside the cave, just before the climb to the first doline; otherwise known as a sinkhole, a doline is when the ground gives way and collapses inwards. In this case, this area of the ceiling was no longer able to hold its own weight and has crumbled down.
As you progress along the cave, you will reach the first major doline, named ‘Watch Out for Dinosaurs’. There are 2 large dolines in Son Doong, with the other one being the ‘Garden of Edam’.
The first doline is connected to the ‘Rat Run’, which is only a couple of hundred metres long and peppered with a few steep climbs. It’s more popularly known as the ‘Green Gours’, a great photo-op spot where water droplets have formed incredible structures over millennia – in this case, a magnificent set of step-like formations – on the cave floor due to the fact that the area has not seen any major flooding over the years, leaving it almost untouched by the elements.
Exiting from the ‘Rat Run’, next is the second and much larger doline, the ‘Garden of Edam’. This doline dwarfs the first, measuring roughly 160m wide and 200m tall. The opening allows plenty of sunlight and rain into the cave system, creating a perfect environment for the growth of a spectacular, vertical jungle.
Expect to be hiking through bushes here, as the foliage is ever-changing due to the harsh elements this area experiences during the rainy season. After traversing through the jungle and down the other side of the doline, you will set up camp with a view into the Garden of Edam.
From here on, headlamps are required, as the next portion of the cave is pitch black. Completely desolate with no greenery, the Passchendaele section is nonetheless home to some very impressive stalagmites, and deeper within, hidden at the back of the cave, lies the Lake of Son Doong. This lake is not actually connected to the Rao Thuong River, which leaves experts wondering where exactly this water came from.
You’ll have to paddle across the lake to reach the next – and final – point: the aptly named ‘Great Wall of Vietnam’, a large 60m wall of muddy calcite. However, the lake is not always present, and at times, you’ll find instead a large expanse of mud, or Passchendaele, which you can choose to waddle through during the dry season between May and July.
From here, the journey ends, as you make your way back to the first doline via a slightly different route through a small oxbow passage above the underground river.
TOURING THE CAVES
Being relatively new, Son Doong is still in immaculate condition with extremely limited tours – and permits – running each year.
So far, the only tour operator licensed to guide visitors through this cave system is Oxalis Adventure Tours (http://oxalis.com.vn), who run both cave expedition and photography tours (5 days each, from US$3,00 per trip), led by members of the British Cave Research Association.
The cave can only be tackled between February and August; it’s closed from September to January due to the treacherous flooding in the wet season. The earliest expedition is only available in 2017, as their 2016 departures are all full up.
Getting there is no walk in the park and involves 50km of jungle and mountain trekking, traversing strong river currents, and climbing 80m using ropes and harnesses, meaning participants have to be very fit to tackle the expedition.
For those with limited time or who prefer less strenuous hikes, there are other cave systems that are easier to access in the area, including the Tu Lan system and the Hang Va system.
Son Doong is accessible via Dong Hoi, which is serviced by regular flights from both Hanoi and Ho Chi Minh City.