Cities of the Underworld S01 E05 Catacombs of Death

Eric finds some knowledgeable guides to take him on a clandestine tour of the catacombs of Paris. Originally a limestone quarry, the vacant space produced its own utility and a rich history in war and in peace to hide things better kept unseen. But the catacombs also represent cracks in the foundation that threaten the stability of the city above the surface.