Secrets Underground

5:00 AM to 6:00 AM
Tuesday 17 September
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Mystery of the Serpent Mound

Season 1 Episode 2 of 8

Rob Nelson investigates mysterious tunnels under Denver's airport, then heads to Ohio to uncover the secrets of a giant serpent-shaped mound

Secrets Underground airs on Discovery Science at 5:00 AM, Tuesday 17 September. (Subtitles.)
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