Four million bodies rest in Rome's subterranean galleries, carved into volcanic tufa between the second and fifth centuries when Christian burial inside the city walls was prohibited by Roman law. The catacombs stretch across 150 hectares beneath the Via Appia Antica, with the Catacombs of San Callisto alone containing sixteen popes and fifty martyrs in labyrinthine corridors that descend four stories into bedrock. What began as private family tombs expanded into vast communal necropolises as Christianity spread through the empire's lower classes, each tunnel wall honeycombed with loculi—rectangular burial niches sealed with marble slabs or terracotta tiles and marked with frescoes of fish, anchors, doves, and the chi-rho monogram. Rome catacombs tour with capuchin crypts packages pair these ancient Christian burial networks with the Capuchin Crypt beneath Santa Maria della Concezione, a Baroque memento mori constructed in 1631 when Capuchin monks transported the skeletal remains of four thousand brothers from their previous monastery. Six chapels display femurs arranged into arched colonnades, vertebrae configured as chandeliers, pelvises and scapulae assembled into floral rosettes, and entire skeletons dressed in Franciscan robes standing in wall niches. The crypt's ceiling inscription—"What you are now, we once were; what we are now, you shall be"—frames the display as theological instruction rather than spectacle, a Counter-Reformation meditation on mortality rendered in human bone. The catacomb tunnels themselves reveal early Christian iconography in its formative phase, before Constantine's legalization shifted imagery from symbolic code to overt narrative. Palm fronds signal martyrdom, peacocks represent resurrection, and the Good Shepherd appears as a beardless youth carrying a lamb—a visual language developed when persecution made explicit religious identification dangerous. Frescoes in the Crypt of the Popes retain traces of Byzantine gold leaf applied during eighth-century restorations, while deeper galleries preserve unaltered second-century work: crude but urgent scenes of Jonah and the whale, Daniel in the lions' den, and the raising of Lazarus. The Via Appia route connected these burial sites to early Christian pilgrimage circuits, and many catacomb complexes contain small basilicas built directly above martyr tombs, where Mass was celebrated on persecution anniversaries. Today's rome catacombs tour with capuchin crypts itineraries operate under Vatican oversight, with entry limited to preserve frescoes degraded by humidity and carbon dioxide from modern foot traffic. The Catacombs of San Callisto open daily except Wednesday, with guided descents required beyond the first level; the Capuchin Crypt maintains separate hours and ticketing at Via Veneto 27. Combined transport options depart from central Rome with archaeological commentary linking the two sites through seventeen centuries of Christian death ritual—from clandestine tufa galleries to Baroque ossuaries designed for public contemplation.