Cities of the Underworld S01E11 - Secret Pagan Underground

Four thousand years ago, a mysterious pagan society called the Hittites dug deep into the soft volcanic rock, called tufa, 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 of Cappadocia?