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9 jaw-dropping caves

By: Catie Leary on June 11, 2010, 1:05 p.m.
Cave of the Swallows

Photo: Stubb/Wikimedia

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Cave of the Swallows

First documented in December 1966, the Cave of the Swallows is a pit cave located in San Luis Potosí, Mexico, that plunges more than 1,400 feet down. It attracts many tourists, especially BASE jumpers and vertical cavers. The cave gets its name from the large number of birds — mainly white-collared swifts and green parakeets — that live within the walls of the cave.