The World's Largest Cave: It Has a Forest, a River, and Clouds Inside

Son Doong, the world’s largest cave, stretches 9 km and contains 38.5 million cubic meters of space. Its enormous passages can accommodate a 40‑story skyscraper, and inside the cave a self‑sustaining ecosystem thrives: a prehistoric rainforest, an underground river, clouds that form within the caverns, and more than 250 endemic plant and animal species, including seven newly discovered ones. The cave’s stalagmites rise like ancient city towers, and phytokarst rocks move toward the sun like semi‑living organisms. Fully explored in 2009, Son Doong remains inaccessible to the public to protect its fragile environment, and the expedition is operated by the authorized agency Oxalis. Note: This video contains a paid promotion. Also, the flooding footage between 2:09 and 2:13 is shot by Ryan Deboodt.