Son Doong Cave: The Spectacular World’s Largest Mountain River Cave

Son Doong Cave (Vietnamese spelling: hang Sơn Đoòng) is the spectacle known as the world’s largest cave. Located in north-central Vietnam, it’s an underground world so vast it has its own unique ecosystem which can form clouds.

Son Doong Cave is part of the Phong Nha – Ke Bang National Park in Quang Binh Province (Quảng Bình), Vietnam. The park also has some more of the largest caves in the world and the oldest karst formation in Asia.

Son Doong Cave as a Masterpiece of Nature

Son Doong Cave Masterpiece
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Son Doong Cave is one of the best caves in Vietnam and worthy of adding to your bucket list. Its beauty and magnificence have been well-covered by international media such as BBC News, CNN Travel, National Geographic, and more. Not to mention, fewer people have conquered Son Doong Cave than have scaled the summit of Fansipan Mountain by foot.

Son Doong Cave was first explored in 2009 and opened to tourism in 2013. One thing to note is that it’s heavily restricted and under international scientific investigation. Therefore, you cannot go there on your own.

Oxalis Adventure is currently the only authorized Son Doong Cave tour operator since 2013. They partner with the British Cave Research Association (BRCA) to ensure international standards are met.

The cave only allows up to 1000 visitors per year so there’s often a long waiting list. However, during the pandemic period, it’s been easier for people living in Vietnam to grab a spot.

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The Colossal Size of Son Doong Cave

Son Doong Cave Size
[ by Oxalis Adventure from Facebook ]

Son Doong Cave is estimated to be about 2 to 5 million years old. That’s actually relatively young compared to the limestone area it’s in which dates back 400 million years.

Nonetheless, it’s currently, since 2010, the largest cave in the world when measured by cross-section. However, the cave is still under further research and exploration by a number of prestigious associations.

The recent data is provided by Oxalis Adventure. Son Doong Cave is over 9 km in length, 200 m in height, and 150 m in width. The total measured volume is estimated to be 38.5 million cubic meters.

For a different perspective, its largest section can fit a Boeing 747 or the great pyramid of Giza in Egypt. Son Doong can also fit the Deer Cave in Malaysia, the world’s second-largest cave, inside it.

How Son Doong Cave Came to Be

Son Doong Cave Pearls
[ by Oxalis Adventure from Facebook ]

As mentioned above, Son Doong Cave was created around 2 to 5 million years ago. This limestone area has Rao Thuong River (Rào Thương) and is part of the Annamite Mountain Range (dãy Trường Sơn).

National Geographic has a very well-made documentary on the second Son Doong Cave expedition in 2010. The team speculated that the river used to flow on the surface level.

However, the ground had a vertical crack which allowed the water to erode the limestone underneath. Additionally, the crack was initially narrow which fortified the cave’s structure and prevented it from collapsing in on itself.

In the last 500 000 years, weak spots on the surface gave way resulting in the two dolines (limestone sinkholes). There was no longer water on the surface so sunlight was able to reach some parts inside the cave.

This paved the way for an ecosystem to begin and thrive in the valleys inside the cave. Son Doong Cave continued to grow in a straight line and gradually became the spectacle it is today.

The Ground-Breaking Discovery of Son Doong Cave

Son Doong Cave History
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Son Doong Cave was first stumbled upon by a local man named Hồ Khánh in 1990. He was making a living exploring the forests near Swallow Cave of Phong Nha – Ke Bang National Park.

At the entrance, he could feel the wind from inside and found an underground river after going down 100 m. However, he didn’t think it was any different from other caves in the area so he soon forgot about it.

Ho Khanh then met Howard and Deb Limbert in 2007. They were part of the British Cave Research Association (BRCA) conducting exploratory caving expeditions in the area. After hearing the story, they urged Ho Khanh to find the cave again.

After many attempts, Ho Khanh succeeded in 2008 and memorized its location. In 2009, he led Howard, Deb, and a team of other caving professionals to conduct the first expedition.

The Expeditions to Study Son Doong Cave

Son Doong Cave Expeditions
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The first expedition had to stop at a 90-meter-high barrier later called the Great Wall of Vietnam. Nonetheless, the team was able to conclude that Son Doong Cave already had the largest cave cross-section to date.

The end of the cave wasn’t found, nor its measurements fully taken, until the second expedition in 2010. In the same year, Son Doong was recognized as the world’s largest cave.

In 2019, a diving expedition was conducted in the underground river of Son Doong.  They found possibilities of it connecting to the one in the nearby Thung Cave. If this is confirmed in the future, it’ll reinforce Son Doong’s status of being the largest cave in the world.

The Origin of the Name Son Doong Cave

Son Doong Cave Origin
[ by Oxalis Adventure from Facebook ]

Before any research, locals used to call Son Doong Cave simply Doong Cave. This was due to the nearby Doong Village (bản Đoòng) of the Bru – Van Kieu (Bru – Vân Kiều) ethnic people.

After the first expedition in 2009, Ho Khanh initially wanted to name the cave after himself. However, after discussion, the team agreed with the name Son Doong Cave.

Sơn means mountain in Sino-Vietnamese and Đoòng is the name of the village. Due to its geographical features, there’s a common misconception that Sơn Đoòng translates to Mountain River.

About the People Behind Son Doong Cave

Son Doong Cave Founder
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Ho Khanh went on to be one of the best guides in Phong Nha – Ke Bang National Park. Currently, he leads a team of over 100 porters for Son Doong expeditions by Oxalis Adventure.

If you want to get to know his story better, he has a homestay café. The Ho Khanh Homestay and Moutain River Café are by the entrance to Phong Nha – Ke Bang National Park.

Howard and Deb Limbert continued to do research around the caves in Phong Nha – Ke Bang National Park. Howard is currently the director of conservation and technical safety for Oxalis Adventure. Also, Deb Limbert is their technical advisor.

Spectacles inside Son Doong Cave

Inside Son Doong Cave
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Son Doong Cave isn’t only famous for its size. Inside the cave is a sublime lost world with its own unique ecosystem and karst formation.

The best season for visiting Son Doong Cave is Spring when the scenery is at its finest. Don’t forget to bring a good camera to capture the best moments of your trip.

Alternatively, there’s another way to explore Son Doong Cave. You can experience the virtual heights of ‘Fly through a colossal cave: Son Doong 360°’ by National Geographic.

Marvelous Karst Formations

Son Doong Cave Stalactites
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After entering Son Doong Cave, you’ll go down a steep slope and artificial lighting is necessary. The first things you’ll see are mineral deposits everywhere.

The stalactites hang from the ceiling and stalagmites rise from the ground in peculiar shapes. In addition, there are flowstone coverings like blankets along the cave walls.

In the first large cavern, you’ll see a stalagmite over 70 meters tall called the Hand of Dog. It may very well be the highest stalagmite in the world.

In the Fossil Passage between the two dolines, you’ll find speleothems (mineral deposits from groundwater) orienting toward the sunlight. This phenomenon is called a phytokarst. In the Green Gours, you’ll further find cave pearls the size of baseballs and mini cave pools.

The Underground River

Son Doong Cave River
[ by Ryan Deboodt from Facebook ]

The first challenge in Son Doong Cave is to traverse the underground river. It’s about 2.5 km in length and quite easy to pass. However, it’s impossible to do this during the rainy season when the water is high and fast. Near the end of the cave, there’s a lake that you will cross on a raft.

One of the best things about a Son Doong Cave tour is that you can actually swim in the water. The underground river is constantly flowing so it’s very clean and refreshing. Of course, you’ll need to follow instructions from your guide. 

The Dolines of Son Doong Cave

Son Doong Cave Dolines
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The two giant dolines with sunlight shining through are a distinctive feature of Son Doong Cave. They were created when the limestone ceiling couldn’t support itself and collapsed.

The first doline is called Watch Out for Dinosaurs and the second one is called the Garden of Edam. The scenery of the first one is usually the subject of many popular photos about Son Doong Cave.

Reaching the second doline, you may just forget that you’re actually inside a cave. This is because it genuinely looks like a forest surrounded by mountains. Its landscape changes depending on the season just like the forest above ground.

Life Thrives in Son Doong Cave

Son Doong Cave Sky
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There’s still little documentation on species inside Son Doong Cave, but that hasn’t stopped the search. The flora inside the cave gathers around the two dolines. It’s similar to the forest above ground due to being connected through wind and rain.

As for fauna, there are many species of monkeys, birds, bats, fish, and insects. An interesting thing about creatures here is that they’ve developed traits to live without sunlight. These include blind fish and some insect species.

Unique Campsites Inside Son Doong Cave

Son Doong Cave Campsites
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Camping inside Son Doong Cave is absolutely one of the best ways to take in the beauty once again. Just sit back, recharge, and relax to the wonder of nature.

The first campsite is after the Hand of Dog and the second is after the Garden of Edam. On clear nights, visitors can watch the starry sky through the dolines.

The Great Wall of Vietnam

Son Doong Cave Great Wall
[ image from ]

Before exiting Son Doong Cave, you’ll face the final and hardest challenge called the Great Wall of Vietnam. To conquer this 90-meter calcite wall, you’ll need proper equipment, instructions, and supervision from your professional guide.

How to Get to Son Doong Cave

How to Get to Son Doong Cave
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To get to Son Doong Cave, you’ll first need to get to Dong Hoi City (Đồng Hới), Quang Binh Province. Oxalis Adventure will provide a roundtrip transfer from Dong Hoi to Phong Nha – Ke Bang National Park.

If you’re in Ho Chi Minh City or Hanoi, you can take a domestic flight directly to Dong Hoi Airport. From Hue, Danang, or Hoi An, you can get a travel bus to Dong Hoi through an agent like Vexere.

If you’re looking for ways to simply visit the national park, it’s a bit different. Check out our article on Phong Nha – Ke Bang National Park for more details.

Oxalis Adventure Caving Tour to Son Doong Cave

Son Doong Cave Adventure
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For reasons including conservation and safety, you can only visit Son Doong according to the schedule provided by Oxalis Adventure. Son Doong Cave tours only run from January to August to avoid the rainy season.

Each year, Son Doong Cave only allows for 1 000 people over 18 years old in groups of 10. Of course, Oxalis Adventure will be in charge of grouping. Rest assured that you can travel with your companion or group if you aren’t alone.

During the pandemic as of 2021, there are more opportunities for people in Vietnam. The waiting list is less competitive and the price may go down slightly. Nonetheless, it’s best to check the information directly by contacting Oxalis Adventure.

The Price of a Son Doong Cave Tour

Son Doong Cave Tour
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A Son Doong Cave tour lasts 4 days plus a prior briefing day on everything you need before departure. The price for one tour may be around 3 000 USD (currently over 68 million VND) per person. However, bargain spots do pop up.

The fee includes the environmental service fee for the management of Phong Nha – Ke Bang National Park. Another part goes to your accompanying team. They have 1 international guide, 1 cave expert,1 forest ranger, 5 safety assistants, 22 porters, and 2 cooks.

Necessary equipment is also provided including 3 LED filming lights. Camping gear includes tents, sleeping mats, pillows, and sleeping bags. Caving gear has helmets, headlights, harnesses, and gloves. A first-aid kit and satellite phone are managed by the guide.

For basic necessities, the guide and porters will bring water filters. All meals during the tour are provided. These include the dinner on the briefing day and breakfast upon check-out after the tour. At the campsite, there is an eco-friendly compost toilet with a toilet seat. The porter team will carry all the gear and prepare all the meals.

As mentioned above, the fee includes a roundtrip transfer and also accommodation. Oxalis Adventure will pick you up anywhere in Dong Hoi City, and you just need to let them know beforehand. Before the tour, you’ll stay at Son Doong Bungalow Homestay.

After returning from Son Doong Cave, you’ll stay at Chay Lap Farmstay & Resort. Transferring to the airport will be arranged based on your flight schedule. If you’re interested in extending your stay in the resort, they can also help with that. They also have more caving tours in Phong Nha – Ke Bang National Park.

Exploring Son Doong Cave Essentials

Son Doong Cave Essentials
[ by Oxalis Adventure from Facebook ]

First off, you’ll need to be physically fit enough to explore Son Doong Cave. It’s advisable to have some experience in trekking or other forms of extensive cardiovascular activities. There will be a lot of rope climbing but you’ll always be under the guidance of the safety team.

The itinerary allows plenty of time for photography and sightseeing so there’s no need to rush. If at some point you can no longer physically continue the trip, you’ll be escorted back outside the cave. From here, you can choose to go back to the city or spend time in the national park.

Here are some essential things to put in your backpack:

  • Suitable clothing for 4-days of physical activity.
  • Good hiking shoes, boots for the rivers, and long socks.
  • Casual clothes for wearing at the campsites.
  • Warm and light jackets (only from February to April)
  • Personal items including toiletries, medication, and bug repellent.
  • Power banks and dry bags for your phone and other personal belongings if necessary.

You can carry part of your luggage and ask a porter to carry one bag of up to 7 kg. However, you’ll only be able to access this bag when you reach the campsites. Oxalis staff will collect and store the luggage that you don’t want to bring along the trip for you.

Son Doong Cave Itinerary

Son Doong Cave Itinerary
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The tour to Son Doong Cave includes 17 km of jungle trekking and 8 km of caving. The itinerary is at the highest difficulty and is subject to change depending on the weather conditions.

Briefing Day

On the briefing day, you’ll need to reach Dong Hoi City before 2 PM. When the time comes, you’ll be transferred to Son Doong Bungalow Homestay. Then, you’ll move to Oxalis Headquarters for a safety briefing and equipment check.

Anyone who doesn’t join this session may be eliminated from the tour without a refund. After dinner, you’ll be transferred back to the homestay.

Day One

On the first morning, you’ll ride a coach for 45 minutes to reach the trailhead. After one hour of trekking the forest along a stream, you’ll reach Doong Village near Son Doong Cave. As mentioned above, this is an ethnic village and you’ll enjoy lunch here.

After about 3 more hours, you’ll reach Swallow Cave (Hang Én) — the third largest cave in the world. After some good swimming in the underground river, you’ll have dinner and camp for the night in this cave.

Day Two

After breakfast on the second day, you go through Swallow Cave and traverse a river for an hour. Then, you’ll head to the top of a hill where you’ll have lunch. Afterward, it’s a couple of short rope climbs to the entrance of Son Doong Cave.

First, you’ll descend to the inside of the cave with safety harnesses. On the way to the first campsite, you can take a refreshing dip in the underground river. Treasure it as this will be your only chance to wash yourself for the day.

As mentioned above, the camp is right after the Hand of Dog. You’ll reach it in the afternoon for a tea break then head to the Fossil Passage. When you return, dinner will most likely be ready for a feast inside Son Doong Cave.

Day Three

The third day begins with some rocky climbs on the way to the first doline — Watch Out for Dinosaurs. After more than an hour of walking, the scenery here makes for an incredible backdrop for lunchtime.

It only takes around 30 minutes to cross the forest that is the Garden of Edam — the second doline. You’ll soon reach the second campsite for a rest before exploring a dry passage with many creepy crawlies.

It’s hard to beat a scrumptious meal after a day of exploring. Savor the campsite dinner because this is the last night you’ll spend inside Son Doong Cave.

Day Four

On the fourth day, you’ll head towards the Great Wall of Vietnam to scale it. After conquering it with ropes and ladders, your reward is a nice lunch on its top. 

Continuing, you’ll cross a passage of more flowstones and cave pearls before emerging into the jungle. From there, you’ll need to make it to the bottom of a hill then hike to the road.

After a drive to Chay Lap Farmstay & Resort, you’ve reached the end of your journey. Feel free to relax by the swimming pool until the group farewell dinner with everyone on the team.

Finally, you only need to sleep well for the night. Also, don’t forget to get ready for check-out at 12 PM the next day.

About Oxalis Adventure

Oxalis Adventure Tours
[ image from ]

Oxalis Adventure is a highly professional tour company founded in 2011. They’re the exclusive operator of tours to Son Doong Cave and Swallow Cave in Phong Nha – Ke Bang National Park.

Additionally, they have a number of tours around Quang Binh including destinations inside the national park. Furthermore, they also run tours of different levels to Tu Lan Cave System (hang Tú Làn), about 70 km away.

They have a team of Vietnamese and international experts including from the British Cave Research Association. Additionally, they follow strict policies on conservation, environment, and safety which can be seen in the Son Doong Cave tour above.

After years of operating, they have developed their website to provide well-presented and detailed information on their tours. You can see what to expect, provided equipment and service, and what to bring for yourself.

Other Popular Caves in Phong Nha – Ke Bang National Park

Other Hiking and Cave Trekking Tours in Phong Nha
[ by Jungle Boss Tours from Facebook ]

Swallow Cave, also managed by Oxalis Adventure, is an excellent and less demanding alternative to Son Doong Cave. In the Dark Cave (hang Tối), available to many operators, you can have fun ziplining, river-dipping, and enjoying natural mudbaths.

There are also a number of beautiful caves in the park that you can explore without a guide. Phong Nha Cave is the longest wet cave in Vietnam with a splendid boat ride to see karst formations. Additionally, Paradise Cave (động Thiên Đường) is the longest dry cave in the world and the inspiration for many photographers.

Phong Nha – Ke Bang National Park is an ideal trekking destination in Vietnam. Furthermore, jungle trekking here can be combined with cave hiking. For these tours, Jungle Boss Tours has a good reputation and the choice of some more exclusive caves.

More Things to do in Phong Nha – Ke Bang National Park

Mooc Springs
[ by Tuyết Minh from Facebook ]

As mentioned above, Son Doong Cave is inside Phong Nha – Ke Bang National Park — a valuable World Heritage Site. It’s one of the most interesting national parks in Vietnam with so much more to enjoy.

Phong Nha Botanical Garden is a preserved and protected area where you can observe about 400 species of flora. It also has easy hikes in the pretty scenery of nature.

Mooc Springs (suối Moọc) is a natural water theme park thanks to the crystal clear water of Mooc Stream. You can also book the Mooc Spring Eco-trail for some wildlife spotting of birds, butterflies, and gibbons.

The area has two main rivers Son (sông Son) and Chay (sông Chày) which have helped shape the park. Tours around Quang Binh by Oxalis Adventure may include a cruise on the Son River and kayaking on the Chay River.

Read more about Phong Nha – Ke Bang National Park

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