The large building was completed in 1786 and is a masterpiece of stereometry and one of the best examples of Baroque architecture of southern Lazio.
It has a polygonal shape, with a hexagonal array and a peripheral wall with12 faces.
The facade has three portals surmounted by lunettes of which the central has a multicoloured mosaic with the figures of St. Peter and St. Cataldo completed in 1966.
The main entrance is a bronze bas-relief by Saverio Ungheri in 1978 and is called the “Door of Hope”.
The sanctuary has a large central dome vault and the interior is decorated with numerous stucco and multicoloured marble. In the choir there is an old organ built in 1764 by Johannes Conradus Werle, that is of great artistic and musical quality.
The chapel of San Cataldo is enclosed by a wrought iron gate and is decorated in faux marble and on the vault is the fresco of “The Glory of San Cataldo” made by Monicelli in 1890. The large wooden statue of San Cataldo, destroyed in a fire in 1870, was rebuilt.