Hang Son Doong
Rank: Top 1000
Wonder Type: Natural
Best of: Cave
Hang Son Doong Cave 'cave of the mountain river' has the largest known cave passage cross-section in the world, and is located near the Laos-Vietnam border. Inside is a large, fast-flowing subterranean river. It was formed in Carboniferous/Permian limestone. Hang Son Doong was found by a local man named Ho Khanh in 1991. The whistling sound of wind and roar of a rushing stream in the cave heard through the entrance as well as the steep descent prevented the local people from entering the cave.
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