Underground Rome, Catacombs and Roman Castles from the port of Civitavecchia

The Basilica of San Clemente is situated some three hundred yards above the Colosseum, on a road that rises gradually to St John Lateran from the valley between the Coelian Hill on the south and the Oppian Hill on the north. It is named after Pope St Clement, the third successor of St Peter in the See of Rome, who died about 100 A.D. Until a hundred years ago, indeed, it was commonly thought that the present church was that to which St Jerome re¬ferred when he wrote about 390 that « a church in Rome preserves the memory of St Cle¬ment to this day ». In 1857, Fr Joseph Mullooly, the then Prior of San Clemente, began excavations under the present basilica, uncovering in the process not only the original, fourth- century basilica directly underneath, but also at a still lower level, the remains of an earlier, first-century building. Later excavations, notably those conducted in 1912-1914 by Fr Louis Nolan when a drain was being built between San Clemente and the Colosseum, show¬ed that underneath this third layer of buildings there was still a fourth stratum, that contain¬ing buildings destroyed in the fire of Nero in 64 A.D. The level, therefore, of the valley in which San Clemente lies was about sixty feet lower in the first century than the present level. After the fire of 64 the gutted buildings were filled in and used as foundations for further houses, at a level that is roughly that of the floor of the Colosseum today.

The catacombs of St. Callixtus are among the greatest and most important of Rome. They originated about the middle of the second century and are part of a cemeterial complex which occupies an area of 90 acres, with a network of galleries about 12 miles long, in four levels, more than twenty meters deep. In it were buried tens of martyrs, 16 popes and very many Christians.