Hang Sơn Đoòng

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

"I was amazed to learn that this cave—translated as Mountain River Cave—is so vast it has its own climate zone: a single passage reaches 655 feet high, 490 feet wide, stretches at least four miles, and has a reported volume of at least 414.4 million square feet, enough room that Google Arts & Culture says a city block of skyscrapers could fit inside. It can even form clouds from its underground river and receives sunlight through two skylights and collapsed-ceiling ‘‘dolines,’’ which have allowed a thriving tropical forest to grow underground; the cave also features towering stalagmites and stalactites, including a 295-foot calcite formation dubbed the "Great Wall of Vietnam," a giant stalagmite called the Hand of Dog, and a doline nicknamed Watch out for Dinosaurs. The cave—whose limestone is believed to be about three million years old and was formed by the Khe Ry and Rao Thunong rivers—was first stumbled upon by Ho Khanh in 1990 and later located by him with Howard Limbert and the British Vietnam Caving Expedition in 2009; it was named Hang Son Doong and earned the Guinness World Record for the world’s largest cave in 2013. The only way to visit is through the tour operator Oxalis, which runs a five-night Son Doong Expedition Tour; the trip is ranked "hard," limited to travelers ages 18–70 with recent heavy trekking experience (including running 5 km in under 50 minutes and climbing five floors continuously), and includes long treks with 2,625 feet of elevation gain, river crossings, rock scrambles, ladders and rope climbs—highlights include the Hand of Dog, the Watch out for Dinosaurs doline, the Great Wall of Vietnam and movie filming sites for Pan and Neverland; the journey costs $3,000 and the next available departures were listed for January 2027." - Rachel Chang Rachel Chang Rachel Chang is a travel and pop culture journalist who contributes to Travel + Leisure, Condé Nast Traveler, Lonely Planet, and more. Travel + Leisure Editorial Guidelines

Best International Destinations for Solo Travel

"The largest natural cave in the world, available for guided tours." - Travel + Leisure Editors

"Spelunking isn’t all about exploring dark, damp places. Case in point: Son Doong. A cave system that boasts the largest passage in the world, Son Doong was first mapped by caving experts less than a decade ago, before it was opened to the public in 2013. It’s difficult to do justice to the immensity of the system, but consider these facts: Some chambers are large enough to house a commercial passenger plane or a 40-story skyscraper; there are numerous microclimates within the complex of caves, and parts are home to subterranean jungles; and not just one but many rivers run through the network. In order to safeguard its structure and unique ecosystem, authorities limit access to this wonder—only 800 permits are granted to visitors each year."