The World's Largest Cave Has Its Own Climate System With Jungles, Rivers, and Clouds—and This Is the Only Way You Can See It

Travel + Leisure

07-07-2025

Ho Khanh was on a mission to hunt for a rare jungle tree Agarwood near the border of Vietnam and Laos in 1990 when a heavy storm pounded down on him, driving the Phong Nha native to find shelter under a cliff. Despite keeping dry, the mountainous columns of fog and cold air that flowed out out of what looked like a cave terrified him, making a serious impression he couldn't shake.
It wasn't until 17 years later when Khanh was on a trip in the Hang En area with Howard Limbert of the The British Vietnam Caving Expedition team that he mentioned the decades-old experience he had—capturing the intrigue of his team. While it took some time to retrace his steps, Khanh managed to lead the team to the exact spot in 2009. They quickly realized that he hadn't just experienced a freakish force of nature, but had actually stumbled into a voluminous cave unlike anything else on the planet.
The team's discovery, which they dubbed Han Son Doong, which translates to Mountain River Cave, quickly garnered global attention, most notably clinching the Guinness World Record title of world's largest cave in 2013.
Impressive in size alone, the single cave passage reaches 655 feet high and 490 feet wide, and stretches a distance of at least four miles, with a volume of at least 414.4 million square feet.
To understand just what that actually means, the cave is so massive it has its own climate zone. And it's so high there's actually room for clouds to form from its own underground river. A city block of skyscrapers could actually fit within it, according to Google Arts & Culture.
Han Son Doong also follows a fault line that's more than 300 feet wide, and does see some sunlight, thanks to two skylights. Plus parts of the ceiling collapsed hundreds of thousands of years ago resulting in 'windows' of sorts called dolines that also let sun in. The result is that so much vegetation thrived that there's also an entire tropical forest growing inside of the cave.
Needless to say, the stalagmites and stalactites here also have other caves beat, none more so than a 295-foot-tall calcite wall that's been referred to as "The Great Wall of Vietnam." The age of the cave's limestone is believed to be about three million years old, formed by two rivers Khe Ry and Rao Thunong, which join at the cave.
The otherworldly site has turned into a stunning destination for adventurers, but the only way to experience it is through the tour operator, Oxalis, which runs a five-night Son Doong Expedition Tour.
While it is open to travelers from ages 18 to 70, it is ranked 'hard' and limited to travelers who have trekked within the last 12 months through variegated terrain at least five miles a day with elevation gain of at least 984 feet. They also must be properly trained, with the ability to run a five kilometers (3.1 miles) in less than 50 minutes, and climb five floors continuously without getting out of breath.
The itinerary includes trekking through forests, with elevation gains of 2,625 feet and crossing multiple rivers, as well as crossing rock scrambles, sandbanks, ladders, and even rope climbs.
But the reward for all the effort is truly unlike any other, with highlights including seeing a giant stalagmite called the Hand of Dog, a doline (the cave windows) called Watch out for Dinosaurs, and of course, the Great Wall of Vietnam. There's even a bit of set-jetting along the way, as one of the points will feature sites where the movies Pan and Neverland filmed.
The journey costs $3,000. At the time of publish, the next availability is for trips departing in January 2027.