6. World’s Biggest Cave

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It wasn’t a geologist or other scientist that discovered the world’s biggest cave, it was a local farmer in Vietnam that found it and then led a British-Vietnamese expidition to its location in 2009. The cave measures 262 by 262 feet in most areas and has a river running through it as well as giant stalagmites that soar 230 feet into the air. The newly-discovered cave, called Son Doong is part of a network of about 150 caves that have not yet been explored. Explorers wonder if even bigger caves are there waiting to be discovered.