The world’s largest cave – Hang Son Doong surpasses imagination by growing bigger!

 “It would be like finding a lump on top of Mount Everest that would make it another 1000 meters higher.”

The title pretty much sums up the case of the largest cave on Earth – Son Doong. Upon its first discovery back in 90s by a local man and the official discovery and exploration back in 2009, Son Doong shocked the world with its incredibly gigantic size, went on to become the biggest cave on the face of the planet and after a very special event in early April 2019 – Son Doong’s underground river diving expedition, the results make it official that Son Doong is actually bigger than we thought!

This surreal revelation has certainly generated hysteria among adventure enthusiasts, travelers, nature lovers and professional cavers worldwide! Read on to find out all the interesting details about this milestone.

Diving Expedition to the underground river of Son Doong – Making history!

In the first week of April 2019, the underground river inside Son Doong cave was dived to a length of -77 m and this made history as the deepest cave dive ever conducted in Vietnam! It was quite a challenge to make more progress, owing to the terribly low visibility of only 2 meters! The beginning of this sump was measured at an astounding depth of -93 m and deepened further ahead.

To be able to dive deeper into the Son Doong Cave, the divers would need to plan a -120 m depth dive and for that, they’ll need to be using a special mixed gases of helium and air. When a dive is to be executed at such a major depth, the level of the challenge dramatically increases and the dives go on for up to 5 hours, which is predominantly done to allow proper decompression.

Due to the use of compressed air, the divers couldn’t dive any deeper as it would expose them to significant risks underground. When spoken to, the diving team said they’ll mostly be coming back in April 2020 to reattempt the dive with all necessary equipment.

About the Son Doong Cave – a unique wonder of the Cave Kingdom

The world’s largest cave, Son Doong, sits majestically in the Phong Nha – Ke Bang National Park, which is one of the best places in Vietnam and also one of the top natural world heritage sites in the world. The jaw-dropping size of Son Doong leaves explorers awestruck and makes them feel like they’ve entered an extraterrestrial world under the surface of the Earth. One of the top reasons to visit Vietnam is a chance to explore this cave by joining the adventure of a lifetime – Son Doong Expedition. Oxalis Adventure – a professional adventure operator in Vietnam which is based in the Phong Nha – Ke Bang National Park as well and is the only qualified (in safety and conservation) official tour operator in the world allowed to conduct expeditions to Son Doong.

This cave is almost 3 million years old and is the ultimate cave experience for adventure and exploration enthusiasts worldwide! It’s not just a cave, but a different and unique underground environment. Son Doong is so huge and has its own jungle, river and even its own climate! It was officially explored in 2009-2010 by the British Cave Research Association (BCRA).

One of the things that put Son Doong at the summit of the top caves to visit in the world is its enormous size; at almost 6km long, with sections reaching up to 200m tall and 150m wide, Son Doong Cave is large enough to house an entire New York City block, complete with 40 story skyscrapers. With a total measured volume of 38.5 million cubic meters, this comfortably surpasses Deer Cave in Malaysia, which was considered to be the previous record holder. After having established an official connection with Hang Thung, another 1.6 million cubic meters of volume would be added to it; this means that Son Doong would enhance its position of the largest cave in the world and continue to prove that it still keeps its mysterious charm alive and remains a secret.

Trending on the news – The world is talking about Son Doong!

This mind-blowing diving expedition in the underground river of the world’s largest cave – Son Doong has caused quite a stir worldwide and has shocked experts, nature lovers with yet another thrilling secret. All major news channels are talking about the trailblazing diving expedition and the fact that Son Doong is still the biggest cave on our planet, but is in fact bigger than we thought! Everyone is also sharing their excitement about what other incredible facts about Son Doong’s size would be revealed when the diving team returns in April 2020 and reattempts the dive.

One of the world’s most renowned media channels, CNN Travel recently released an article about this glorious discovery and also shared a video showing the world the might of the Son Doong cave. CNN also got a chance to interact with Howard Limbert, who was the leader of the first caving team that discovered and explored the Son Doong cave and he is also the Technical Director of Oxalis Adventure.

When in conversation with CNN Travel, Howard Limbert exclaimed that “It would be like finding a lump on top of Mount Everest that would make it another 1000 meters higher.” He also added that “Any cave in the world could comfortably fit inside Son Doong when it’s connected – the size is just outrageous!”

Popular websites like Travel & Leisure and News.com.au have called this a ‘groundbreaking discovery’ and have been widely spreading the word through interesting articles and videos, along with giants like MSN and Kids.com.au expressing their awe at the extraordinary discovery of Son Doong Cave’s outrageous size. The entire science and travel news community can’t contain their excitement about Son Doong and Hang Thung’s mysterious underground connection, what’s to come when the divers return in 2020 and are brilliantly telling the world about the wonders hidden inside the Phong Nha – Ke Bang National Park of Vietnam.

Exclusive journey to the world’s largest cave – Hang Son Doong!

This incredible Son Doong Cave Expedition will give you a wonderful chance to explore the world’s largest cave and exit via the Great Wall of Vietnam. This is the only tour available of Son Doong Cave by the official tour operator Oxalis Adventure Tours.

This exclusive journey requires more than 25 porters, safety advisors & guides. You will explore the entire length of Son Doong Cave, Hang En Cave, and visit Ban Doong ethnic minority village.

Imagine trekking straight into the depths of the world’s largest cave which can fit a Boeing 747 flying through the largest passage, on an expedition unlike any other. Son Doong Cave is a masterpiece of nature with otherworldly landscapes, enormous stalagmites and statuesque stalactites – hanging from the ceiling and rising from the ground like an alien species. The real jungle inside the cave will amaze you in every way, while misty clouds envelope the scene. The fossil passage will give you the opportunity to understand the formation of this ancient limestone.



  • Climb the Great Wall Of Vietnam
  • 2 nights camping inside Son Doong Cave (largest cave in the world)
  • 1 night camping in Hang En Cave (third largest).
  • Portable lighting equipment to capture stunning photographs
  • 25km of Jungle Trekking and 9km of Caving
  • Visit Ban Doong Ethnic Minority Village


An adventure from start to finish, you will use ropes to climb into the entrance, and climb up the Great Wall of Vietnam, a calcite wall totaling 90m in height. You will always be under the guidance of the Oxalis safety team.

The Expedition is not a race, so you should not expect to rush on this tour. There will be plenty of time for photography and to explore the cave. However, all adventurers are expected to be fit, and have some previous trekking experience (not necessarily climbing or caving experience).

There are places remain available for trips departing in 2019 and 2020. Please make your reservation here or contact us at [email protected] for details.

Oxalis Adventure Tours:


If you are seeking a taste of the caves and really don’t have enough time then we recommend a one-day cave and jungle trek. We currently have three tour options for you to select, each with a slightly different style and suitability.

• Phong Nha National Park 1-DayOur family adventure in the Phong Nha offers a great taste of untouched jungle and impressive wild caves. It is the easiest level of adventure but there is still 5km of trekking and 2km of caving, and optional swimming during warmer weather into one cave. It’s suitable for kids from 12 and above with good fitness, and so this makes for a great day for everyone! It costs VND 1,650,000 per person (USD 72).

• Tu Lan Experience – 1 DayThis is one of our original one-day tours and still one of the best adventures in Vietnam. This one-day tour includes rock scrambling, 50m swimming through a wild river-cave, and up to 9 km of trekking through the lush jungles. You will also strap yourself in for a 15m descent down a ladder. It costs VND 1,800,000 (USD 78) per person.

• Hang Tien Discovery – 1 DayThis one-day tour is perfect for trekking enthusiasts eager to see the largest cave of Tu Lan but without time for the two-day experience. Hang Tien is a dry cave so no swimming required, but still includes up to 4km of trekking through mostly flat jungle and about 500m exploring this incredible cave that will no doubt impress with its grandeur. It costs VND 2,000,000 per person (USD 87).


Our most popular cave adventures start from two-days providing an immersive jungle and caving adventure, each targeting a slightly different kind of adventure-seeker, or perfect for those who want to combine a couple of tours to see different caves and areas on one trip to Phong Nha.

• Tu Lan Cave Encounter – 2 DaysOur most popular tour exploring the famous jungle area of Tu Lan. On this overnight camping excursion, you will trek through a number of different dry caves, swim up to 500m through a couple of river caves, witness outstanding cascading waterfalls underground as featured in National Geographic, and spend the night at our jungle camp beside a gorgeous waterfall. It includes 12km of trekking and 3km of caving in total and is for those with a good adventurous spirit. It costs VND 5,500,000 per person (USD 239).

• Hang En Cave Adventure – 2 DaysFor two days, this is our best-value-for-money tour that includes one of the most jaw-dropping natural landscapes you will see in this lifetime. This cave is considered the second largest cave in Vietnam and third largest in the World, and it also makes up one night of the original five-day Son Doong Cave Expedition being so close to the largest cave in the world. It includes visiting Ban Doong Ethnic Village, located in the jungle, and a magnificent campsite on a sandy beach inside the cave. It includes 22km of jungle trekking at times quite rocky, multiple knee-deep river crossings, and elevation change of 400m (the ‘hill’ you won’t forget), and 4km of caving. This is a level 3 adventure on a scale of 1 to 6. It costs VND 7,600,000 per person (USD 330).

• Hang Tien Endeavor – 2 DaysA two-day trek into the jungle to see the largest dry cave of the Tu Lan area, exploring 5.5km of this truly stunning cave, with a variety of karst formations. This 13km trek is suitable for those not too keen on cave swimming or too many hills, but still up for an adventure. This is a level 4 adventure between 1 and 6, with 6 being the most challenging. It costs VND 6,500,000 per person (USD 283).

• Hang Va Expedition – 2 DaysA technically challenging, but equally rewarding two-day caving adventure in the heart of Phong Nha National Park. This tour takes you deep into the jungle to one of the most spectacular river-caves, with formations not seen anywhere else in the world! It involves rock scrambling, wading through an underground river, bouldering and rope-traversing within the cave, to reach the rarest tower cone formations. This involves quite a lot of technical work due to safety, but is not overly difficult, it includes 10km of trekking and 3 km of caving.  This is a level 4 adventure, with 6 being the highest. It costs VND 8,000,000 per person (USD 348).


Now, if you really want to increase the adventure and soak up the wild jungle of Vietnam, with plenty of time to relax and enjoy the area, we highly recommend a three-day caving tour of our Tu Lan or Hang Tien.

• Wild Tu Lan Cave Explorer – 3 DaysThis tour incorporates the very best of Tu Lan with two different jungle campsites besides stunning waterfalls, 3km of cave exploring through a number of caves, 1km of cave swimming and visiting some additional areas not included on our shorter experiences. Our three-day tour is very popular and tends to be booked out so get in quick to enjoy this thrilling jungle adventure. It includes 17 km of jungle trekking and with quite a bit of swimming you will need to have a good level of fitness. It is not for the faint-hearted, but still only considered level 3 adventure level compared to level 4 of the Hang Tien 3-day tour. It costs VND 8,000,000 per person (USD 348).

• Hang Tien Exploration – 3 DaysThis three-day tour stands out for combining a taste of Tu Lan with some river cave swimming, before crossing a mountain range to reach the valley for Hang Tien – the most astounding dry caves in the region, where you will enjoy trekking, bouldering over various rocky terrains to witnessing breathtaking patterned calcite walls & ceilings of Hang Tien. It’s challenging and definitely more suited to adventure enthusiasts who have trekking experience and prefer more challenging routes. It includes a total of 22km of trekking, 6.5 km of caving and an elevation change of 150m over one particular hillside. You will get wet, you will be challenged, but you will not be disappointed. Hang Tien is located adjacent to the Tu Lan area so you will enjoy the best of both worlds – a level 4 adventure out of 6 adventure levels. It costs VND 8,500,000 per person (USD 370).


For those looking for the ultimate adventure experience in Vietnam, and thriving for the real grand expedition of the world, you should opt for these 4-day journeys to explore the entire cave system of Tu Lan and the largest cave on Earth

• Tu Lan Expedition – 4 DaysYou will also explore all of the extraordinary caves in Tu Lan, including Kim Cave and Secret Cave that boasts phenomenal natural falls and karst formations inside these two unbelievable river caves. Complete a trek through Hang Tien Cave – famed for its vastness and magnificent formations. Our secluded jungle campsites are spectacular and mostly different from those visited on our shorter treks in the same region. This is a perfect alternative expedition for those who are unable to do Son Doong Expedition, still it’s challenging and not recommended for those without experience. It includes an additional night at Chay Lap Farmstay before the tour to ensure you are well rested and ready to depart early the following day. Level 5 on our 6 adventure levels. It includes 30km of jungle trekking, 5 km of caving, about 800m swimming through caves and one abseil in a cave in the pitch black – highly adventurous! It costs VND 15,000,000 per person (USD 652).

• Son Doong Expedition – 4 DaysBy now you would have seen some pictures of Son Doong Cave, and even they don’t do it justice. The record-breaking Son Doong Cave is hands-down one of the most stunning places on this planet Earth. The expedition is tough, but not too difficult so long as you have a strong resolve to achieve. It is surely one of the newest wonders of the world. Son Doong is not just another cave tour – it is life-changing to say the least. It includes 25km of trekking, 9 km caving including rope climbs, and the 90m ascent of the Great Wall of Vietnam using a ladder, elevation change of 400m and many river crossings inside and outside the cave. Level 6 on our adventure levels. It costs VND 69,800,000 per person (USD 3000).

STILL HAVE QUESTIONS?  Visit our FAQs section where we have a lot of answers for your questions and concerns. https://oxalis.com.vn/faq-general/

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