Note: This basilica is located near the Coliseum (Coloseum) and the site of gladiator barracks. The basilica stands on what originally was a Christian house of worship in the 1st century A.D. In the courtyard of the house stood a Mithraic altar. Mithraism, in ancient Rome, was favored by emperors Commodus and Diocletian.

St. Clement was a contemporary of Peter and Paul (perhaps) and he was banished to Crimea where he was martyred by orders of emperor Trajan (98-117A.D.). Some say that his relics were rescued by St. Cyril and brought back to Rome. This current basilica is among the oldest and stands on a basilica built in the 4th century by emperor Constatine. Another basilica arose following the devastation of Rome by the Normans under Robert Guiscard in 1084.