Son Doong Cave

Son Doong is a natural cave formation in Quảng Bình in central Vietnam. The underground passages run for more than 9 kilometers through massive limestone rock, with the main gallery reaching over 200 meters in height and 150 meters in width in some sections.

A local resident named Ho Khanh came across the cave entrance in 1991 while searching the jungle for agarwood. British researchers conducted the first full exploration only in 2009, mapping the entire extent of the underground chambers.

The name Son Doong comes from Vietnamese and means mountain river cave, a reference to how water carved through limestone over millions of years. Visitors today experience a cave with its own weather patterns, where mist drifts through chambers and the air remains constantly humid.

Visits require a permit and take place only with authorized guides from Oxalis Adventure Tours, as the cave sits within a protected national park. Expeditions run from January through August, before the rainy season begins and underground rivers make access impossible.

Two large ceiling openings let sunlight penetrate deep inside, leading to the growth of an underground forest with trees reaching 50 meters tall. These areas of natural light are called dolines by guides and researchers, and they support vegetation normally found only on the surface.