Hang Sơn Đoòng

Hang Sơn Đoòng is a vast limestone cave in Vietnam’s Phong Nha–Kẻ Bàng National Park, known for enormous passages, underground rivers, and jungle-filled collapsed chambers.

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Phong Nha–Kẻ Bàng National Park: A protected landscape in central Vietnam containing extensive limestone karst, forests, and cave systems. The cave lies within this UNESCO-listed national park and its karst landscape.
Underground river: A watercourse that flows partly or entirely beneath Earth’s surface. A river flows through Sơn Đoòng, shaping passages and linking its underground drainage.
Hồ Khanh: A Vietnamese forest worker and local guide who encountered Hang Sơn Đoòng before its formal exploration. His earlier encounter led him to guide the expedition that surveyed the cave.
Adventure tourism: Travel involving physically demanding activities in natural environments. Sơn Đoòng is accessed through tightly managed expedition tourism.
Great Wall of Vietnam: A massive calcite barrier inside Hang Sơn Đoòng, rising across part of the cave passage. This formation became a landmark obstacle during the cave’s early exploration.
Karst: A landscape formed as soluble rock dissolves, producing features such as caves, sinkholes, and underground drainage. The limestone terrain around Sơn Đoòng is a classic karst landscape.
Sinkhole: A depression or hole formed when surface material collapses or dissolves into underlying ground. Sinkholes and related openings connect the cave’s passages with the surface.
British Cave Research Association: A British organization that supports cave science, exploration, and surveying. Its expedition team surveyed Sơn Đoòng with Hồ Khanh in 2009.
Oxalis Adventure: A Vietnamese adventure-tourism company that operates licensed expeditions to Hang Sơn Đoòng. It manages the limited tours that bring visitors into the cave.
Doline: A closed depression in karst terrain, often formed by dissolution or collapse. Large roof openings in Sơn Đoòng create sunlit dolines within its passages.