Basilica di San Clemente

Lonely Planet review

A short walk up from the Colosseum, this fascinating basilica provides a vivid glimpse into Rome's multilayered past. Through the courtyard, the 12th-century church at street level was built over a 4th-century church, which, in turn, was constructed over a 2nd-century pagan temple and 1st-century Roman house. Beneath all that are foundations dating to the Roman Republic.

In the medieval church, it's the stunning 12th-century apse mosaic that steals the limelight. It depicts the Trionfo della Croce (Triumph of the Cross), with 12 doves symbolising the apostles and a crowd of bystanders including the Madonna, St John, St John the Baptist and other saints. Renaissance frescoes in the chapel of St Catherine, by Masolino and his student Masaccio, recount scenes from the life of the saint, who was strapped to a wheel and tortured to death (hence the circular firework named after her). The high marble pulpit on the left was added when the new church was built.

The 4th-century church below, the basilica inferiore, was mostly destroyed by Norman invaders in 1084, but some faded 11th-century frescoes remain, illustrating the life of St Clement. According to legend, the 1st-century Pope Clement (who, it is believed, was born Jewish) was banished to the Crimea and forced to work in the mines. His preaching among the other prisoners caused the Romans to bind him to an anchor and throw him into the Black Sea. The water receded some time later, revealing a tomb containing Clement's body. Thereafter, the tomb would be revealed once a year, when the waters miraculously receded.

Descend further and you'll find yourself walking an ancient lane leading to the Roman house and dark temple of Mithras, which contains an altar depicting the god slaying a bull. Don't be alarmed by the sound of running water: it's an underground river flowing through a Republican-era drain.