Ancient Aliens

Sometimes the strangest things on Earth...Are happening just below its surface. From tunnels carved by giant sloths to desperate attempts to stop the dead from rising again - these are the weird and wonderous tales of the sea beasts, hidden cities and impossible creatures that lurk beneath us.
Thank you to our experts who contributed to this episode: Austin Rogers, Sabina Magliocco, Greg Jackson, Brandy Shillace, Mitch Horowitz, Kathleen Tracy, Cord Whitaker, Don Wildman, Joseph Dituri, Rebecca Lieb, Hakeen Oluseyi, David Mizejewski, Sami Jarroush, Jason Horton, Ramy Romany, and Kavitha Davidson.
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Giorgio Tsoukalos explores ancient structures that defy conventional explanation.
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Many of the architectural marvels of the ancient world bear striking similarities to one another, even though they were built by civilizations that were separated by thousands of miles and are believed to have had no contact with one another.
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From Egypt to Easter Island, towering figures built by ancient man stand watch over the Earth. Are these stone giants simply a testament to humanity’s past or could they depict visitors from another world?
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A 1952 memo surfaces about a top-secret U.S. government group tasked with investigating UFOs.
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