St. Paul's is the largest patriarchal basilica in Rome after St. Peter's. A church was erected here by Constantine at the beginning of the 4th century. However, it was only of modest proportions as it had to be squeezed in between Via Ostiense, an extremely important commercial artery, and the cemetery where St. Paul was buried. Ostensibly, the Emperor did not want to create any more friction with the population that was still largely pagan.
At the end of the 4th century, this small church was replaced with a second basilica possessing the same shape and dimensions as today's basilica. This new church was consecrated in 390 and, over the centuries, it was enriched with the works of important artists. However, on the night between July 15 and 16, 1823, it was completely destroyed by fire.
After this dramatic event, the commission nominated by Pope Leo XII decided to have the church rebuilt in the same form and with the same dimensions as before.
This new St Paul's, consecrated in 1854 by Pope Pius IX, is therefore a faithful copy of the ancient basilica and the only one in Rome which is still a typical paleochristian church. Christian churches were originally based on the pagan basilicas used for civic purposes and comprised a succession of spaces designed to be used during the progressive stages followed by converts before they could fully practice their faith.
The quadriporticus, designed for the catechumens, was where Baptism was administered and the atrium was where preparation was made to receive the sacrament of communion. Not until after they had completed this spiritual journey were the faithful admitted to the church proper. The interior had the shape of a Latin cross, the cross of Christ.
The enormous dimensions of the ancient churches served to show that the new religion was not reserved for a small elite but, on the contrary, able to welcome everybody. It should be noted that, at the time when Christianity was legalized, only 15% of the population had been converted.
Pietro Cavallini's mosaic dating back to the Middle Ages and covering the façade was almost completely destroyed in the 1823 fire. This had to be replaced with works made in the Vatican School of Mosaics.
Luckily, however, although other mosaics—those on the Triumphal Arch from the V century and others in the apse from the 13th century- were seriously damaged, they were able to be restored.
The ciborium, which both Arnolfo di Cambio and Cavallini had worked together on, is still the original; so too is the candelabrum which holds the Paschal candle, a 12th century work signed by Pietro Vassalletto. This same artist designed the extraordinary cloister.