I stepped through a narrow passageway and into a small room with thick stone walls. The warm, humid air weighed on my lungs with the mustiness of centuries past. The tour guide, a thin young man from California with Harry Potter glasses, who was living in Rome to study Latin, led the group past rows of pagan crypts, and as I peered through the openings that had been cut away in the stone, I saw some had hollowed-out spaces in the walls for crematory urns, while others housed elaborately carved sarcophagi. The guide shared the detailed history of the site, from 64 A.D. when Saint Peter was killed on the…