Secrets Underground

1:00 AM to 2:00 AM
Tuesday 13 January
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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 Channel at 1:00 AM, Tuesday 13 January. (Subtitles.)
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