The Hang Son Doong cave in Vietnam, located in Quang Binh Province within Phong Nha-Ke Bang National Park currently holds the title as the largest known cave in the world. With dimensions exceeding three miles (5 km) in length and 660 feet (200 m) in height, this natural wonder could house 15 Great Pyramids of Giza within its vast chambers. Its enormous passages are so spacious that a Boeing 747 could hypothetically fly through parts of the cave. The unique “skylights” in the cave’s limestone structure allow sunlight to flood in, nourishing two jungles nestled within the cave, and creating an ecosystem unlike any other on Earth.

A Discovery Decades in the Making

As per a recent report by LiveScience, Hang Son Doong, meaning “Mountain River,” was first discovered by Ho Khanh, a local resident, in 1990. Khanh stumbled upon the cave while hunting, noting the rush of wind and sound of water echoing from inside. However, surrounded by dense foliage, he was unable to relocate it until 2009. That year, Khanh successfully led a team from the British Cave Research Association, including cave expert Howard Limbert, to its entrance. Limbert, technical director at Oxalis Adventure, which now organises tours of Son Doong, described the discovery as monumental, with the team quickly recognising its scale and significance.

A Cave of Record-Breaking Dimensions

Upon detailed exploration, researchers determined that Hang Son Doong has a total volume of around 1.35 billion cubic feet (38.5 million cubic metres). This makes it the largest natural cave ever measured. In 2019, divers found an underwater tunnel connecting Son Doong to Hang Thung, adding another 57 million cubic feet (1.6 million cubic metres) to its volume. Limbert compared the discovery to “finding an additional peak on Mount Everest,” underscoring the cave’s unmatched scale in the subterranean world.

A Natural Masterpiece and Ecosystem

Beyond its size, Son Doong features remarkable geological formations. It houses one of the world’s tallest stalagmites, standing 260 feet (80 m) high, and includes the Great Wall of Vietnam, a calcite barrier that challenged explorers on their initial visits. The cave’s fossil passages offer a glimpse into the area’s ancient marine history, with fossils from sea creatures that once inhabited the region. Inside the Passchendaele Passage, named after a World War I battlefield, explorers encounter muddy terrain that mirrors the historic battlefield’s conditions.

In the heart of the cave, the collapsed ceiling forms skylights that allow light to reach its depths, nurturing thriving jungles and completing the surreal landscape of Son Doong.