Cities of the Underworld

Season 1, Episode 12: Secret Pagan Underground

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4000 years ago, a mysterious pagan society called the Hittites dug deep into the soft volcanic rock to carve out an intricate underworld. But after almost 800 years of rule, the Hittite Empire vanished without a trace. Where did their people go and what clues have they left behind in their complex subterranean world?