This 2019 episode notes that the Catacombs contain the bones of an estimated 6 to 7 million people, and explains that their history is really two interconnected stories of mines and human remains.

Melitta Bentz and the Coffee Filter
39:22

SYMHC Classics: COINTELPRO 2
41:29

Behind the Scenes Minis: Whoopsy Whimsy
24:41