The Catacombs of San Callisto extend four levels beneath Via Appia Antica, holding nearly half a million Christian burials across twenty kilometres of tunnels carved into volcanic tuff between the second and fifth centuries. Pope Callixtus I established the site as the official cemetery of the Roman Church in 218 AD, and nine pontiffs rest in the Crypt of the Popes, their Greek and Latin epitaphs still legible on marble slabs. Above ground, the Via Appia Antica remains the world's oldest paved road, commissioned by Censor Appius Claudius Caecus in 312 BC to link Rome with Brindisi on the Adriatic coast. Its original basalt paving stones bear the grooves of two millennia of cart wheels, and fragments of imperial tombs line both sides, including the cylindrical mausoleum of Cecilia Metella, a noblewoman whose fortress-tower has stood since the first century BC. Modern visitors combine a Rome catacombs tour & Appian Way itinerary because both sites occupy the same archaeological corridor south of the Aurelian Walls. The catacombs close every Wednesday for conservation work, and guided descents last forty-five minutes, passing through galleries decorated with early Christian frescoes of anchors, fish, and the Good Shepherd. The Crypt of Santa Cecilia preserves a copy of Stefano Maderno's sculpture marking the spot where the saint's body was discovered in 820 AD. Temperature underground holds steady at twelve degrees Celsius year-round. The Appian Way corridor includes three major aqueduct ruins—Aqua Claudia, Aqua Marcia, and Aqua Felice—their brick arches crossing the plain between the catacombs and the Parco della Caffarella. Electric bike tours cover twelve to fifteen kilometres, stopping at the Circus of Maxentius, a fourth-century chariot track that could seat ten thousand spectators, and the Villa dei Quintili, a sprawling imperial estate with baths, nymphaeum, and amphitheatre. Golf cart options navigate the cobbled sections for visitors who prefer not to cycle. All tours include timed entry to the catacombs, bypassing the ticketing queue at Via Appia Antica 110, where standard admission costs 10 EUR and opening hours run 09:00 to 12:00 and 14:00 to 17:00 daily except Wednesdays.