Today finds us in a jewel box of a church, one whose embellishment over the last 1400 years comes harmoniously together in the glory of the God Who has been worshiped on this site since the early days of the Church of Rome. St. Clement, from whom this church takes its name, is believed to have been the fourth pope. While certain details are scantly, it seems likely that he was either a freed slave or son of a freed slave who had been a member of the Imperial household. Clement wrote a letter to the Corinthians, with the authenticity of other writings being held in doubt by many. Tradition relates that he was banished to the Crimea by the Emperor Trajan, where he continued the work of evangelization. As a result of this, he was sentenced to death by being tied to an anchor and thrown into the sea. It seems that his relics were recovered and buried nearby, where they would later be found with the anchor by St. Cyril.
As we can see, this church has a long history. Even before the legalization of Christianity, a house on the site was joined to neighboring buildings to create a church that served as the home of the Titulis Clementis. This was replaced with a larger basilica just over a century later, being complete by 390. This was renovated in 533-535, including the addition of a chancel screen and schola. An especially noteworthy event occurred with the return of the relics of St. Clement from the East. They were brought to the city by Ss. Cyril and Methodius, the Apostles to the Slavs, on their mission to Rome in 867, and enshrined here by Pope Adrian II. Two year later, in 869, St. Cyril passed away in this city, and his relics were likewise enshrined here soon thereafter.
As with the rest of this area, the Norman attack of 1084 reduced this church to ruins. While the church remained serviceable, even hosting the election of Paschal II in 1099, rebuilding was of grave necessity. When the rubble from the destruction was spread out it raised the level of the ground several feet, and so it was on this higher level that the new St. Clement’s began to take form. Dedicated on 26 May 1128, it would receive repeated renovations over the next several centuries. Soon after its completion the apse mosaic was added, followed by the decoration in the chapel of St. Catherine of Alexandria. Further renovations followed in the early eighteenth century. One of the most important developments here, however, is not architectural at all, but rather archeological. In 1857, the rector, Fr. Joseph Mullooly, began excavating under the floor of the current church, and found the remains of both the older basilica and even older remains from the classical period. Although flooding made work difficult, a new drainage trench alleviated these problems, and today the excavations under the church are some of the most interesting in the city.