Son Doong Cave Deep Dive
Hang Son Doong — "Mountain River Cave" — in Vietnam's Quang Binh province is the largest cave passage in the world by cross-section. The main passage measures up to 200 m high and 150 m wide, and 9 km long; the cave contains internal jungle, clouds, and rivers.
Discovery and exploration
Local farmer Ho Khanh found the cave entrance in 1991 but lost track of it. He relocated it in 2008 and led the British Cave Research Association expedition under Howard and Deb Limbert to explore it in April 2009. The expedition reached "the Great Wall of Vietnam" — a 90-m calcite flowstone barrier — before turning back; subsequent expeditions found a way past.
The dolines
Two huge dolines (collapsed cave ceilings) admit sunlight and support internal rainforest in the cave. The first doline, "Watch Out for Dinosaurs," holds a jungle floor with trees 30+ m tall. The second contains the famous "Garden of Edam."
Internal weather
The cave is large enough to have its own weather. Cold air from the cave interior meets warm humid air entering through the dolines, producing visible cloud formations that drift through the chamber. Localised rain falls on the cave floor in damp months.
Tour access
Oxalis Adventure Tours holds the sole concession. Approximately 1,000 visitor permits per year are issued at USD 3,000 per person for the 4-day expedition. Bookings open annually and sell out within days. The tour involves crossing rivers, scrambling, camping, and traversing the Great Wall by rope.
Conservation
The Phong Nha-Ke Bang National Park (UNESCO 2003, extended 2015) manages the cave under strict access limits. The Oxalis monopoly is controversial among cavers but has effectively limited visitor impact.
Explore on the map
See Son Doong on the interactive map.