In the province of Quang Binh, in central Vietnam, there is a cave so large it has its own weather. Clouds that form inside the cavity, an underground river that runs through it from end to end and a jungle that grows in its interior, fed by light pouring in through two enormous collapses in the roof. It is called Son Doong and it is, according to official measurements, the largest cave in the world.
But Son Doong is not an isolated anomaly. It sits within Phong Nha-Ke Bang National Park, a karst area of more than 2,000 km² that harbours hundreds of caves, many of them still unexplored. This park, a UNESCO World Heritage Site, is the global epicentre of large-scale caving: caves measured not in metres but in kilometres, with ceilings exceeding 100 metres and galleries that could fit a 40-storey building.
Vietnam is not the first destination that comes to mind when you think of caves. But for anyone interested in the underground world, from the casual visitor to the professional caver, this country offers something found nowhere else on the planet. Over the next sections you will find the five caves that best prove it, how much each visit costs, which ones can be seen without any experience, when to go and how to reach Phong Nha-Ke Bang National Park.
Son Doong: the cave that defies the imagination
Hang Son Doong was discovered in 1990 by Ho Khanh, a local woodcutter who took shelter from a storm at the entrance to the cavity. The noise of the underground river and the wind blowing out of the opening kept him from going further than the first few metres. The cave was forgotten for nearly two decades.
In 2009, a British-Vietnamese expedition led by caver Howard Limbert relocated the entrance with Ho Khanh’s help and carried out the first complete exploration. The measurements confirmed what seemed impossible: the main passage was more than 5 kilometres long, up to 200 metres wide and reached a maximum height of over 200 metres, according to the official Oxalis Adventure website, the only operator authorised to run expeditions.
Son Doong’s total volume was estimated at 38.5 million cubic metres, a figure that made it the cave with the largest known volume on the planet. In 2013, Guinness World Records officially recognised it as the world’s largest natural cave.
But the numbers do not convey the experience. What makes Son Doong unique is what lies inside. At two points in the ceiling the karst collapsed thousands of years ago, opening natural skylights through which direct sunlight pours in. That light has allowed a tropical jungle to grow inside the cave, with trees up to 30 metres tall and animals that live permanently underground: monkeys, snakes and birds. It is the only known place where a forest thrives inside a cavity.
A river runs the full length of the main passage, and during the rainy season its level can rise by several metres. That watercourse is what has carved the cave over millions of years and what keeps shaping it today. At one point a calcite wall almost 90 metres high, known as the Great Wall of Vietnam, blocks the way: visitors climb it with ropes and harnesses to continue. And in the pools of standing water lie some of the largest cave pearls ever found, calcite spheres formed drop by drop over thousands of years.
Only 1,000 people a year are allowed to visit Son Doong. The expedition lasts 4 days and 3 nights, costs around 3,000 dollars per person and includes guides, porters, technical equipment and camping inside the cave. Places sell out months in advance.
Paradise Cave: the underground palace
If Son Doong is the cave of records, Paradise Cave (Thien Duong) is the cave of accessible beauty. Discovered in 2005 and opened to the public in 2010, it is the longest dry cave in Asia, with more than 31 kilometres explored.
What visitors can see is a section of approximately 1 kilometre, fitted with lit walkways running through a gallery up to 72 metres high and 150 metres wide. The stalactite and stalagmite formations are of a density and variety hard to find in any other show cave in the world: calcite curtains that look like fabric, columns ranging in colour from white to amber, and formations the water is still actively shaping.
For the more adventurous, there is an extended 7-kilometre tour that ventures into the unlit galleries, requires head torches and allows you to see the cave in its natural state.
Paradise Cave is open every day from 7:00 to 16:00 and admission starts at 250,000 VND (about 10 euros). It is the most visited cave in the park and the ideal option for anyone who wants a spectacular experience without an expedition.
Hang En: sleeping inside a giant cave
Hang En (the Swallow Cave) is the third largest cave in the world by volume. Its main entrance reaches 110 metres in height and the ceiling rises to 145 metres at its highest point. Inside, a crystal-clear stream flows over a sandy beach where visitors set up camp for the night.
The Hang En tour is a 2-day, 1-night expedition that includes a full day’s trek through the jungle, crossing rivers and passing through the village of Ban Doong, home to the Bru-Van Kieu people. The experience of sleeping inside a cave of these dimensions, with the light from the entrance illuminating the gallery at dawn, is one of the most memorable you can have in Vietnam.
Hang Va: the conical stalagmites
Hang Va is a smaller cave but with a geological formation unique in the world: fields of conical stalagmites that rise from the floor in perfectly regular shapes, as though someone had sculpted them. These formations are the result of a particular crystallisation process that only occurs under very specific conditions of humidity and temperature.
Access to Hang Va requires swimming through flooded galleries, scrambling over rock formations and using harnesses on the technical sections. It is not a cave for casual tourists, but for caving enthusiasts it is one of the most rewarding experiences in the park.
Phong Nha Cave: where it all began
The cave that gives the park its name is Phong Nha, a river cave explored by boat along an underground river. It is the oldest cave in the park in tourist terms (it has been visited for decades) and the most accessible: the standard 1,000-metre route is done sitting in a rowing boat, with no need to walk.
For those who want to go further, there is a 4,500-metre kayak tour that penetrates the cave’s deeper galleries, where the stalactite formations are older and the silence is absolute.
Getting there and planning your visit
The gateway to all these caves is Dong Hoi, the capital of Quang Binh province. It has an airport with direct flights from Hanoi (just over an hour and a half) and Ho Chi Minh City, and it is a stop on the north-south railway line. From there, the village of Phong Nha is about 45 kilometres away, a little under an hour by car or bus. It is worth staying in Phong Nha itself: it concentrates the agencies, the transfers to the caves and the restaurants, and it saves you long drives every morning.
Not every cave demands the same effort. The expeditions to Son Doong and Hang En require good fitness, several days of trekking and are not suitable for young children. Paradise Cave and Phong Nha Cave, on the other hand, are easy to visit with a family: the first has lit walkways and stairs, and the second is explored sitting in a boat. They are the best choice if you are travelling with children or want a relaxed half-day visit. To understand what you are looking at underground, it helps to know how caves are formed and where their stalactites and stalagmites come from.
From the karst of Vietnam to that of Mallorca
The caves of Vietnam and the Cuevas dels Hams share the same origin: the dissolution of limestone by water. The karst process that carved Son Doong over millions of years is the same one that shaped the galleries of the Cuevas dels Hams, in Porto Cristo. The difference is one of scale: the limestone at Phong Nha reaches 1,000 metres thick and has endured intense tropical rainfall for longer, which explains the colossal size of its cavities.
You do not need to travel to the other side of the world to see that same phenomenon at work. At the Cuevas dels Hams you can walk through formations born of the same geological process, sail across the Sea of Venice lake and enjoy a live classical music concert on the water. Check the timetables and book your tickets on the official Cuevas dels Hams website. And if you want to keep exploring the underground world, take a look at the ice caves of Iceland, another example of how water sculpts impossible landscapes.
Frequently asked questions about the caves of Vietnam
How much does it cost to visit Son Doong?
The 4-day expedition costs around 3,000 dollars per person and includes guides, porters, equipment, meals and camping inside the cave. Only 1,000 visitors are allowed per year and places are booked months in advance. The sole authorised operator is Oxalis Adventure.
Can you visit any cave in Phong Nha without an expedition?
Yes. Paradise Cave and Phong Nha Cave are accessible to any visitor with no caving experience or special equipment needed. Paradise Cave has lit walkways and Phong Nha Cave is explored by boat. Both are open all year round.
When is the best time to visit the caves of Vietnam?
From February to August. The rainy season (September–November) can cause flooding that temporarily closes some caves, especially those with underground rivers. March to May offers the best balance of good weather and fewer tourists.
Is it true they have discovered a cave bigger than Son Doong?
On a recent expedition, Howard Limbert’s team discovered a new cave in the same park with an estimated volume of 38.5 million m³, dimensions similar to or larger than Son Doong. Researchers are investigating whether the two cavities are connected by an underground passage, which would form the most extensive known cave system on the planet.
Vietnam is a reminder that the underground world still holds uncharted territory, places where jungles grow below ground and rivers write the rock as they please. Not everyone can sleep inside Son Doong, but you can start much closer to home: underground, in Porto Cristo, the same force that carved these giant caverns is still at work in the Cuevas dels Hams.