The original document, which initiated the building of the Church was issued by Pope Paul I on 2nd June, 761. The Church was built to receive the venerated remains of early Christian saints who were buried in the Catacombs. There are two marble tablets at the entrance to the Church on which are inscribed the names of some of the saints and martyrs who are buried in the Church.
The original Church was built in the style of the ancient basilicas: a central nave and two side aisles with a row of pillars on either side. The style and structure of the Church has changed somewhat throughout the centuries. The typical Roman tower was added during the renovation of the early 12th. Century. The reconstruction of the Church to its present-day appearance dates from 1523 – 1534. The ornamentation of the interior by Mattia de Rossi was completed in 1689 giving the church that quality of unity amid variety so representative of the late baroque period.
The paintings in the church date from the 17th and 18th centuries.
The Facade of the Church was reconstructed in 1703. The four baroque statues – viewed from the Piazza – are: San Silvestro by Lorenzo OUone, Saint Stephen by Michelangelo Borgognone, Saint Clare by Giuseppe Mazzoni and Saint Francis by Vincenzo Felice. (In Capite): The title «In Capite» refers to the relic of the head of Saint John the Baptist, which is kept in the first side chapel to the left as you enter the Church. Parts of the reliquarv date from the 13th and 14th centuries.