Son Doong Cave: how to visit Vietnam’s otherworldly giant

Deep in Vietnam, tucked among mountains and jungle, there is a cave that feels almost unreal. It is called Son Doong, and it holds the title of the largest cave on the planet. The scale is disorienting: a plane could fly through sections of it, trees have taken root in places, and clouds sometimes gather—inside the cave.

How it was found

The cave came to light by chance. In the early 1990s, a local man named Ho Khanh stumbled upon a strange opening in the rock, where the sound of water mixed with a steady wind. He was frightened and chose not to enter. Only nearly two decades later, in 2009, did a team of British explorers descend, concluding that this was not just a large cavern—it was the largest known on Earth.

Since then, Son Doong has become a sensation. It stretches roughly 9 kilometers in length, with walls soaring up to 200 meters. To put that in perspective, one of its chambers could accommodate a 40-story skyscraper.

What lies inside

Son Doong runs through limestone mountains. Over many years, water carved through the rock, gradually creating the cave. Sunlight filters in through several large openings in the ceiling, which is why trees managed to grow beneath the surface. With the moisture and the temperature inside, mists sometimes form as well.

Life inside the cave

The cave is not only enormous—it is alive. Inside it shelters rare plants, insects, and fungi that you will not encounter outside. Researchers say places like this help reveal how life can develop in near isolation, without sunlight or familiar weather patterns.

Can you go there?

In theory, yes—but it is far from simple. Since 2014, access has been limited to organized groups run by a single operator, Oxalis Adventure. Independent trips are not allowed.

Visitor numbers remain small: over ten years, about 7,500 people from more than 50 countries have been inside. Timing is restricted too: entry is allowed only from February to August; after that, rising water levels make conditions hazardous.

Demand is enormous. For 2025, every slot has already been claimed, and only bookings for 2026 are still available.

Why protecting it matters

The cave is fragile. Any disturbance—trash, excessive light, a careless step—can damage what nature built over millions of years. That is why access is tightly managed, routes are designed down to the details, and every group undergoes special preparation.

It is a rare example of tourism and conservation moving in step. For now, the balance holds: the cave is open to the world, yet cared for with restraint.

Research continues

Scientists believe Son Doong may be only part of a much more complex system, potentially connected to other underground caves. Much inside remains unstudied. Future expeditions may reveal new passages, chambers, or even new animal species.

Beyond charting how such landscapes form, Son Doong is helping to illuminate the planet’s past—a kind of key to Earth’s ancient history.