How a local hunter found the world's largest cave (twice)

The short version

Son Doong was not found by a scientist or a satellite. It was found in 1990 by a local logger named Ho Khanh, who ducked out of a storm and felt cold wind roaring out of a hole in the jungle floor. He never went in, lost the spot for almost two decades, and only in 2008 managed to find it again. In 2009 he led a British caving team to the entrance, and within a year the survey confirmed it: the largest cave passage on earth, sitting in the hills above his home village the whole time.

If you ride into Phong Nha today and wonder why a quiet farming district has hostels, cafes and tour offices on every corner, this is the answer. One man, one cave, one very long wait to find it twice.

Ho Khanh, the man who walked these forests for a living

Ho Khanh grew up in Phong Nha and made his living the way most men in the village did in the 1980s and 1990s: in the forest. He logged, he hunted, and he searched for agarwood, the fragrant resinous wood that was worth real money to anyone willing to spend days deep in the jungle to find it. The karst hills that are now a protected national park were simply his workplace.

That matters to the story. Ho Khanh was not lost or lucky. He knew these mountains the way you know your own street. He knew which cave mouths the hunters used for shelter, where the streams ran, which ridges to cross. So when he stumbled on something he had never seen before, he noticed.

1990: a storm, and wind coming out of the ground

The date the cavers later settled on is 10 December 1990. Ho Khanh was out looking for wood when a storm rolled in, and he ducked toward a cliff to wait it out. Near the base he found an opening in the ground he had never registered before, and two things stopped him.

First, the wind. Cold air was pouring out of the hole, strong and steady, the kind of draught that only comes from a very large empty space underground. Second, the sound: from somewhere far below, the boom of running water, an underground river he could hear but not see. He did not climb down. The opening was steep and slick, the storm was on him, and he had no rope and no reason to risk it. He fixed what he could of the route in his memory and carried on with his day.

Then life happened. The exact line back to that one hole, in a forest full of cliffs and sinks that all look alike, slipped away from him. He could not have known he had just found the biggest cave on the planet. For years it stayed a half-memory, one strange spot among hundreds he had passed.

The British cavers and the cave nobody could find

From the early 1990s, a team of British cavers, organised around Howard and Deb Limbert and working with Vietnamese partners, had been systematically exploring the caves of Quang Binh province. Over the years they mapped hundreds of them. Part of the method was simple: talk to the local hunters and loggers, the men who actually walked the forest, and ask what they had seen.

Ho Khanh told them about the cave with the freezing wind and the river you could hear roaring inside. The cavers knew exactly what that combination usually means, and they asked him to take them there. He could not. He went back to look for it, more than once, over years. The forest did not give it up. Around 2000 he tried again at their urging and still came back empty. The cave he had found by accident now refused to be found on purpose.

This is the part that makes the discovery story honest rather than tidy. Finding Son Doong the first time took a storm and a coincidence. Finding it the second time took roughly eighteen years of failing.

2008: found again, and finally entered

In 2008 it clicked. On one more trip into the forest Ho Khanh relocated the entrance, and this time he marked it properly so it could not slip away again. He got word to the Limberts that he had it.

In April 2009 he led the British caving team to the spot and down inside. Peter MacNab was among the first through the entrance, and what the team walked into stopped them cold. The passage was so wide and so high their lights could not reach the far walls or the roof. There was a forest growing inside, fed by light from collapsed sections of ceiling called dolines, with its own clouds and its own weather. They named the cave Son Doong, after the Doong village and the mountain it sits behind.

They did not finish that first trip. Deep into the cave they hit a wall of glistening calcite around 60m high, blocking the way on. They called it the Great Wall of Vietnam, and in 2009 they had no way past it. They turned back knowing the cave kept going, and that nobody yet knew how far.

2010: over the wall, and a world record

The team came back in 2010 with the gear to climb. On 17 March 2010 they got over the Great Wall of Vietnam, pushed to the end of the passage, and completed the survey. The numbers were absurd in the best way. Son Doong ran roughly 9km, with the main passage up to 200m high and 150m wide, and a volume around 38.5 million cubic metres. A Boeing 747 could fly through the largest section without clipping a wing.

That made it, by passage volume, the largest cave on earth, comfortably bigger than the previous record holder in Malaysia. Guinness World Records confirmed it in 2013, and a National Geographic feature in 2014 put those impossible photographs in front of the world. After that, Phong Nha was no longer a secret.

9km

Main passage length surveyed

200m

Tallest passage height

38.5M m³

Volume, largest cave on earth

2013

Guinness World Records confirmed it

What it all turned into

The cave is run on a tight leash, and that is deliberate. Only one operator, Oxalis, holds the licence, and only about 1,000 people are allowed inside in an entire year. The four-day, three-night expedition costs around $3,000 (79,500,000 VND, prices checked June 2026), which sounds steep until you see the size of the team of guides, safety staff and porters it takes to move you through safely. If you cannot get a spot or cannot stretch to the price, the bookable giants nearby are the honest answer: Hang En at around $333 (8,800,000 VND) with Oxalis, who hold that licence too, or Hang Pygmy, the world's fourth largest cave, at around $310 (7,900,000 VND) with Jungle Boss, who you can usually book for this season. Prices checked June 2026.

Ho Khanh got his due. He became part of the operation that runs the cave he found, and he opened a homestay in Phong Nha that he still runs today. The income from those capped expeditions flows back into local guiding and porter work, which is a large part of why the village grew the way it did.

So next time you ride the main strip and pass a homestay sign with the name Ho Khanh on it, slow down for a second. The reason you can be here at all, the reason this valley has a tourism economy, is a hunter who felt a cold wind in a storm, lost the spot for eighteen years, and refused to stop looking.