What the Largest Cave on Earth Looks Like From Inside
Hidden inside Vietnam’s Phong Nha-Ke Bang National Park is Son Doong, the largest cave on Earth. It’s so vast that a Boeing 747 could fit through its chambers. Inside, jungles grow beneath openings in the ceiling, clouds drift through the darkness, and rivers flow across limestone that’s millions of years old. It feels like an untouched world within our own.
The Accidental Discovery
Image via Wikimedia Commons/Dave Bunnell
The discovery of Son Doong was pure chance. In 1990, a local villager named Ho Khanh stumbled upon the cave while taking shelter from a storm. From deep inside, he heard the roar of water and felt powerful gusts of wind rushing out of the darkness. Startled, he left, and for nearly twenty years, he couldn’t find the entrance again.
Then in 2009, he finally retraced his steps and guided a team of British explorers, led by Howard Limbert, back to the spot. What they uncovered was staggering: a cave nearly nine kilometers long, 200 meters high, and wide enough to swallow a 40-story building. That same year, Son Doong was officially recognized as the largest natural cave on Earth, with a volume of roughly 38.5 million cubic meters.
World Inside The Earth
Stepping into Son Doong feels like entering another planet. Some chambers are so large that a Boeing 747 could fly through them. Sunlight pours through two enormous sinkholes where the cave’s roof collapsed thousands of years ago. Beneath those openings, entire jungles thrive. Trees reach over 100 feet tall, vines crawl along the walls, and mist drifts through the air. Explorers call one of these lush sections the Garden of Edam, where ferns and tall trees grow beneath the skylight.
Beyond the forest, the cave’s formations look otherworldly. Towering stalagmites climb up to 260 feet, including the famous Hand of Dog, shaped like a giant paw. At the far end, the Great Wall of Vietnam rises nearly 300 feet, a calcite wall so steep that explorers had to return a year later with climbing gear to reach the top. Fossil passages contain ancient corals and shells, reminders of the time when this region lay beneath the sea.
A Cave That Makes Its Own Weather
Image via iStockphoto/Geng Xu
Son Doong has a rare natural feature: its own weather. The cave’s size and underground river create clouds, fog, and even rain inside. Temperatures usually stay between 60°F and 77°F, cooler than the jungle above. In summer, vapor rises from the river and forms drifting clouds while waterfalls stream from the openings above. Winter brings cold winds sweeping through its tunnels, and from January to April, beams of sunlight cut through the mist, lighting up the chambers in breathtaking ways.
Visiting The Hidden World
Reaching Son Doong takes effort, and that’s part of what keeps it pristine. Only one company, Oxalis Adventure, is licensed to run tours. Each expedition lasts six days and five nights and costs around $3,000 per person. Visitors hike through thick jungle, cross rivers, and camp inside the cave. Group sizes are small, and tours are limited each year to protect the ecosystem.
Most travelers stay in Phong Nha village or Dong Hoi city before the trek. Once there, many explore other nearby caves such as Paradise Cave, Dark Cave, and Phong Nha Cave, which are easier to reach but still stunning in their own right.
Standing inside Son Doong, surrounded by mist, echoing water, and walls that stretch far above the ground, it’s easy to forget you’re still on Earth. This underground world shows every visitor how vast and mysterious nature can be, and how a single discovery can change what we know about the planet.