• Established in the 3rd century AD, the Catacombs of St. Callixtus span over 20 km and include the tombs of 16 popes and many early Christian martyrs.
• Key highlights include the Crypt of the Popes, frescoes, burial chambers, and ancient Christian symbols like the Chi-Rho and fish.
• Open Thursday to Tuesday, 9am–12pm and 2pm–5pm; access is by guided tour only, with tickets priced between €10–€15.
• Located along the Appian Way, it's easily reachable via Metro A to San Giovanni and Bus 118 or 218, or by bike or taxi.
• Wear modest clothing and sturdy shoes; the tour involves stairs, narrow tunnels, and cool underground temperatures around 15°C.
San Callisto Catacombs