How to Trek Through Son Doong Cave in Vietnam
Son Doong Cave is unlike anywhere we’ve ever been – so vast it has its own weather system, with clouds and mist swirling inside the cave like something out of a dream. Formed over millions of years by underground rivers carving through limestone along a fault line, Son Doong was only fully explored in 2009 and is still revealing secrets today. From jungles thriving under collapsed ceilings to underground rivers you can swim through, trekking Son Doong feels like stepping into a lost world.
Backpacking here is a once-in-a-lifetime adventure, only available as a guided tour with Oxalis Adventure. It’s a six-day experience, including four days of trekking and three nights spent camping in the cave. You’ll scramble over massive boulders, harness up for climbs, wade through plenty of water crossings, and sleep within view of dolines where the jungle thrives. It’s the kind of journey made for thrill-seekers and nature lovers who crave something truly wild and untouched.
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How can you explore Son Doong?
How difficult is trekking through Son Doong?
How safe is trekking through Son Doong?
How to train for a trek through Son Doong
What is Son Doong Cave?
Son Doong Cave is the world’s largest cave by volume, located in Vietnam’s Phong Nha-Kẻ Bàng National Park. It has chambers that reach up to 200 meters high and 150 meters wide, and it’s estimated to be about five times larger than what was previously considered the largest known cave – Deer Cave in Maylasia.
For a sense of scale, Son Doong is large enough that it could fit skyscrapers and airplanes inside of it!
The history of Son Doong
Son Doong Cave was formed along a tectonic fault line in the Annamite Mountains in central Vietnam. It was formed over two to five million years ago due to underground rivers eroding the limestone along the fault line.
Roughly 300,000 years ago, the cave’s ceiling has collapsed, forming large skylight openings, called dolines. These dolines are incredibly beautiful, allowing sunlight to enter and letting the jungle flourish from inside the cave.
A local hunter, Hồ Khanh, discovered Son Doong in 1991 but did not venture inside due to the steep descent. It wasn’t until 2009 that he helped guide British cavers there, and guided treks did not start until 2013.
What’s exciting is that there are still parts of Son Doong yet to be discovered. Oxalis Adventure and the British caving team are participating in ongoing expeditions today. On our trip, our safety guide, Dai, talked of scuba diving missions to explore other passages!
How can you explore Son Doong?
The only way to explore Son Doong is through a guided expedition with Oxalis Adventure, the exclusive tour operator.
Independent exploration is not allowed due to the cave’s fragile ecosystem, rough terrain, and conservation efforts.
Our tour group
When can you hike here?
The trekking season runs from January to August. The cave is closed from September to December due to flooding from the monsoon season.
The cave features its own weather system, creating distinct conditions as the seasons change. Inside the cave remains cool year-round, ranging from 22°C to 25°C (72°F to 77°F), although the outside temperature and humidity fluctuates throughout the year. Each season is beautiful and has its own benefits.
For up-to-date weather conditions, check here.
Spring: January to March
Temperature:
15°C to 22°C (59°F to 72°F)
Potential for cool winds in the cave
Highlights:
Waterfalls early in the season
Occasional sunbeams in March
Seasonal lake
Floating on the lake above stalactites
Late spring to early summer: April to May
Temperature:
23°C to 30°C (73°F to 86°F)
Highlights:
Especially lush green landscapes
Blooming flowers
Clouds and mist form inside the cave
Clouds beginning to form at the top of the cave
Summer: June to August
Temperature:
30°C to 36°C (86°F to 97°F)
Highlights:
The water crossings and swimming in the caves feels the most refreshing
Tours during this time are often available less than one year out
Trail statistics
Trail information: Oxalis Adventure
Distance: 25 km (15 miles)
Elevation Gain: 800 m (2,625 feet)
Duration: Six-night trip, including four days of hiking, three nights of camping, and lodge stays at the start and end of the tour
Difficulty: Very strenuous. Obstacles include slippery, uneven ground, scrambling, light rock climbing, and river crossings
Source: Oxalis Adventure
Age requirements
Participants must be between 18 and 70 years old, weigh under 100 kg (220 lbs.), be in good physical condition, and pass a health screening by Oxalis Adventure.
How difficult is the tour of Son Doong?
Oxalis Adventure labels each of their tours by difficulty. The tour of Son Doong is their most strenuous – a level six. It includes trekking between 11 and 5 km (7 to 3 miles), with 300 m (984 feet) of elevation gain or loss each day of the hike through Son Doong.
If you struggle to make it to the first campsite, you will be escorted back to Phong Nha the following day without a refund.
Slippery trails
What is the hike like?
Hiking into the cave is downhill through slippery mud with river crossings. Once you’re in the cave, you’ll do some walking, lots of scrambling on and through large rocks, and some climbing with knotted ropes and climbing gear. The hike out of the cave is steep, downhill, and slippery with sharp rocks. Nearly every step of this trek is calculated. Read more on it here in our trek itinerary.
Fear of heights
The climb up the Great Wall of Vietnam is the only section of the trek through Son Doong that may frighten someone with a fear of heights. It is a 90-meter (295 foot tall) wall that Oxalis has split into three sections – a ladder and two pitches (roped sections).
To reach the wall, you’ll either walk through mud or be rowed across a seasonal lake to the ladder at the base of the wall. Without the lake present, the ladder is 18 meters (60 feet) tall. At this point in the hike, you’ll be wearing a full body climbing harness. After the guides help you rope up, you’ll begin your climb up the ladder. If you have a fear of heights or suffer from vertigo, focus on climbing up the ladder, looking upwards, and you’ll do just fine.
Once at the top of the ladder, you’ll need to climb uphill a few more steps to a flat area. It’s a good distance from the edge. Here our guides encouraged us to rest before starting the second, smaller pitch to the top of the wall.
Claustrophobia
When we tell people we backpacked through a cave, one of the most common responses is, “I could never do that; I’m claustrophobic”. However, claustrophobia is not a problem in Son Doong. The entire passageway through the cave is enormous, and each night you’ll camp near a cave entrance. or doline, so you’ll see daylight.
How safe is the tour of Son Doong?
We felt that the tour through Son Doong was extremely safe. Each tour is equipped with one tour guide, one safety guide, and six safety assistants. Considering each tour has ten guests, that means there is a guide or safety assistant for every two guests. They are always ready to lend a steady hand, mention where good footholds are, and are always there when you need them.
Communication
On your trek there will be no phone signal or Wi-Fi; however, the guides will be equipped with a satellite phone to keep in touch with the operations team in case of emergency.
Safety equipment
Oxalis uses international standard equipment, mainly imported from France, the UK, and Switzerland, that is selected, inspected, and maintained by cave experts from the British – Vietnamese Cave Association. The tour guides and safety crew are responsible for equipping you and operating all the climbing gear.
River crossings
The depth of water and currents of river crossings vary by season. During our hike in March, most water crossings were no higher than calf deep, with a few thigh-high crossings (for 5’4” Meghann, anyway).
For shallow crossings, we often held hands to help steady one another while walking across the slippery river rocks and linked arms together to cross in deeper water. If you don’t have a partner with you on the tour, ask a safety assistant to help you cross if you feel unsteady (they’ll likely offer without you asking).
The guides did mention that at times one river crossing could be as high as your hips. If that’s the case, they’d use a rope to help cross.
Wildlife
Leeches
There are a handful of small creatures to be wary of during your trek through Son Doong. First, there are the leeches. Wear the socks we have linked in our packing list and check for leeches on your clothing upon exiting the jungle (they only live in the jungle, not the caves), and you shouldn’t have a problem with them.
Creepy crawlies
Centipedes, spiders, and scorpions live in the cave as well. You'll be storing your wet shoes outside of your tent overnight – smack them together to get rid of unwanted creatures that may have found their way in before putting them on.
Bats
You’ll also see bats in the cave. There is no need to worry about rabies – they’ve been extensively tested. They only live in the darker areas of the cave, not near the entrances and dolines where you’ll be camping. We loved seeing them fly nearby while we were hiking, and they never bothered us.
Bugs
You need to be wary of the flying bugs that are the size of fruit flies. These bugs were in the darkest sections of the cave and were attracted to the light of our headlamps. Aim your light up a bit higher so they stay out of your eyes. If they land in your eyes, blink them out instead of rubbing. Rubbing your eyes with these bugs in them will cause pain.
Snakes
There are 60 venomous snakes in Vietnam. Although we were a bit wary of this before our trip, our guides said they’ve only seen one snake on a tour. They also said the snakes fear us and want to stay away from us just as much as we do them. The odds of encountering one are negligible.
Birds
Although harmless, our least favorite animal in the caves were the swallows that live in the entrance of Hang En (where you’ll camp the first night). The swallows nest in the cave in the colder months, returning to the cave in the late evening and leaving again by mid-morning.
Unfortunately, the birds poop everywhere when they’re inside the cave for the night! Put your shoes upside down outside of your tent to dry, do not leave your tent open, and wear a hat if you’d like to keep your hair poo-free. If the chance of getting pooped on really bothers you, you can hang out in the covered dining area.
The Hang En Campsite
Plants
On your trek the guides will point out one poisonous plant that is similar to poisonous ivy. It grows by rivers and was always very easy for us to avoid. If you do make the mistake of touching it, it would hurt. Even worse, getting the contact site wet makes it worse, so you’re unable to shower for days.
Sudden rain or floods
Son Doong Cave is affected by monsoon rains that generally happen between September and December, when tours are not running. Certain areas, like the Hang En campsite, flood. In case of sudden rain or floods, Oxalis has backup plans, backup routes, and safety routes throughout Son Doong. There is a stash of emergency food at each campsite, and Oxalis is always monitoring weather forecasts.
Rafting to the Hang En campsite
Injuries
Oxalis’s team of guides, cave experts, and safety guides are trained in first aid, rescue techniques, and hauling systems.
If you were to get injured, the team does their best to help you stay on the tour by providing first aid. If your injury or medical issue is more serious, even requiring evacuation, the team is prepared to carry out anyone who is unable to exit on their own. There are no helicopter evacuations available in this part of Vietnam.
Dehydration
Staying hydrated in a hot, humid environment is imperative. Drinking water alone is not enough to prevent hypernatremia – you also need to replace electrolytes throughout your hike. Check out our packing list for our favorite electrolytes.
How to train for a trek through Son Doong
Hiking and regular activities
Oxalis Adventure suggests hiking, engaging in regular sports, or walking or running 4-5 km (2.5-3 miles) 3-4 times a week to prepare for the hike. As for the elevation gain, they say you should be able to climb five flights of stairs continuously without becoming out of breath or dizzy.
We’re of the mindset that more training is generally better. The more hiking (or other exercise) you do, the more enjoyable the hike will be.
Scrambling down to camp
Overnight trips
To prepare for the trip, Oxalis also requires you to do one overnight-trek (backpacking trip) in the year leading up to your tour. This helps you prepare to camp in the wilderness and sustain vigorous activity multiple days in a row. We’ve got a beginner’s guide to backpacking with tons of tips here.
Scrambling
A huge portion of the trek through Son Doong is scrambling over large rocks. The irregular movement will make you sore in odd places and tires out knees. We found trekking here was like hiking the boulder field on Mount St. Helens.
You’ll always have safety guides near to lend you a steady hand or point out a foothold as well. We both found comfort in following their footsteps whenever it was slippery, which was often.
Other good rules of scrambling are:
Test rocks out before putting your weight on them to ensure that they’re steady.
Use three points of contact – meaning that you should have three limbs steadying yourself while the fourth (hand or foot) moves to a knew hold in tricky spots.
The scramble down to the first nights campsite
Climbing
Although we are amateur climbers, we thought it was helpful (but not required) to have some climbing experience. Try out a climbing gym or try a guided climb outdoors to practice finding holds and gain experience repelling.
How much does it cost?
The Son Doong Expedition Tour costs $3,000 USD or 75,000,000 VND per person. After applying, you’ll be vetted for your fitness and capabilities. If accepted, 100% of the payment is due to reserve your place.
Rescheduling
Oxalis allows you to reschedule your tour date if there are spots available. Considering most of the people on our tour booked a year out, finding an opening with shorter notice would be difficult.
Cancellations
Cancellations made 90 days before your tour departure will receive a 100% refund, minus a $274 USD, or 7,000,000 VND, fee. If you cancel within 45 days of your departure, you’ll be charged 50% of the tour fee, and if you cancel with less than 45 days before your departure, you’ll be charged 100% of the tour fee.
What is included?
Guides and porters
Tour guide
Safety expert
Six safety assistants
One chef
15+ porters
The supporting team and guests on our tour
Safety equipment
Helmets
Caving headlamps
Extra caving headlamp batteries
Climbing gear
Satellite phones
First aid kits
Camping gear
Composting toilets
Stocked with toilet paper
The toilets use rice husks to eliminate odors
After microbial composting, all waste is brought to designated composting pits in the jungle for decomposition
Handwashing stations
Changing stations
Clothing drying stations
Saunas
The following gear is labelled so you have the same camping gear each night:
Tent
Sleeping bag
Pillow
Sleeping pads
Dry bag
Trekking gear
Oxalis has the following equipment available to borrow:
Jungle boots
Sizes 36-46 EU
Backpacks
Water bottles
Meals
You’re provided dinner at the safety briefing in Phong Nha, three generous meals a day while on the trek, a group dinner post-trek at the Chày Lập Farmstay, and breakfast the following morning.
Filtered water
Dietary restrictions accommodations
Oxalis easily accommodated Meghann’s celiac disease (gluten free) and a handful of vegetarians on our tour
Make dietary restrictions known in advance
Some of the best meals we ate in Vietnam were inside the cave!
Accommodations
The night before your trek you’ll stay at the Commander Lodge
The day you finish your trek you’ll stay at the Chày Lập Farmstay
While you’re trekking, Oxalis will stow and transfer your luggage from the Commander Lodge to the Chày Lập Farmstay (they label and stow valuables in a safe as well)
Chày Lập Farmstay
Transportation
Oxalis provides transportation to and from Phong Nha from Dong Hoi. To reach Dong Hoi, we suggest flying into the regional Dong Hoi Airport (VDH) or taking a sleeper train or bus there.
Travel insurance
Oxalis provides basic travel insurance included in their tour of Son Doong. It covers accidents that occur on the tour and care is provided in a basic Vietnamese hospital.
The maximum coverage is 50,000,000 VND per case (approximately $2,000 USD). If you’d like additional coverage, we’d suggest using World Nomads.
Conservation
A large portion of the tour cost goes directly to the conservation efforts in Phong Nha-Kẻ Bàng National Park, a UNESCO World Heritage Site. Conservation efforts go towards education, wildlife protection, forest protection and management, and more (Source: Oxalis Adventure).
How far in advance should you book a tour?
Tours to Son Doong Cave are limited to 1,000 visitors per year to protect its ecosystem. Tours book up quickly, so it’s best to book a year in advance to secure a spot.
If you’re unsure of your travel dates, keep an eye on Oxalis’s booking calendar to watch when dates begin to fill up. Trips to Son Doong are limited to groups of ten, and the calendar will show how many slots are left for each trip.
Eco-tourism
Sustainability
Oxalis is doing a great job prioritizing sustainability. They’re working closely with local authorities and conservationists to maintain Phong Nha-Kẻ Bàng National Park while developing sustainable eco-tourism. They limit the frequency and size of tours, allow the area to have regeneration periods, and they have a goal to be net zero by 2030.
Economic development
Moreover, the tourism from the caves has significantly supported the town of Phong Nha from the devastating impact the Vietnam/American War had on the Quảng Bình Province. Since it was part of the Ho Chi Minh Trail, Phong Nha suffered repeated bombings. On average, every square meter of land in the province was exposed to 65 pounds of explosives – you’ll see evidence of this and the people's resilience in town and on your tour of Son Doong (Source: Peace Trees Vietnam and Oxalis Adventure).
Since then, Oxalis Adventure has created over 500 local jobs and helped improve Phong Nha’s infrastructure. People who were previously logging or hunting have found work in tourism, allowing the jungle and wildlife to rebound. There’s even been a documentary made about it by Emmy Award-winning filmmaker Sid Perou – check it out here.
All in all, this is tourism you can feel good about.
What to pack
There is so much to consider when packing for Son Doong. You’ll want to prioritize purchasing trekking shoes, wool socks, and lightweight trekking clothing. We’ve got another blog with recommendations and tips here.
Other Oxalis Adventure tours
If the Son Doong Cave Expedition isn’t available, Oxalis Adventure has several other tours, including easy day tours and other overnight expeditions.
We’re especially intrigued by the moderate two-day, one-night Hang Va Expedition Tour and the demanding six-day, five-night Tu Lan Cave Expedition, although they have a total of 15 tours to consider.
Search the blog for more adventures! Try searching for topics such as “backpacking”, “waterfalls”, or “national parks”.