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Some Ancient Astronaut Theorists believe alien life could be found deep within the earth's most mysterious caves in this clip from Season 9, "Forbidden Caves". #AncientAliens
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"Ancient Aliens" explores the controversial theory that extraterrestrials have visited Earth for millions of years.

HISTORY® is the leading destination for award-winning original series and specials that connect viewers with history in an informative, immersive, and entertaining manner across all platforms. The network’s all-original programming slate features a roster of hit series, premium documentaries, and scripted event programming.