Cities of the Underworld (2007)

S1E5 Catacombs of Death

Eric enlists the help of experienced guides for a secretive exploration of the Parisian catacombs. Once a limestone quarry, this underground labyrinth holds a wealth of history, serving both as a refuge during wartime and a place for secrets best left concealed. However, beneath its historic allure, the catacombs reveal fissures in the city's structural integrity, posing a looming threat to the world above.