What great mysteries lurk unseen beneath your very feet…?
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Presenting the most mysterious underground places on Earth, including Chauvet Cave and its strange cave art; Belize’s Actun Tunichil Muknal cave and its Mayan sacrifices; the medieval Erdstall of Europe; Turkey’s massive underground city Derinkuyu; and the strange megalithic underground temple of Malta, the Hypogeum of Hal-Saflieni.