Founded by Pietro, priest from Illiria, between 422 and 432, on an antique "Titulus Sabinae" probably raised in the house of a Sabina matron that then ended up identifying itself with the saint with the same name from Umbria. In 824 the "Schola Cantorum" was added up, by the hand of Pope Eugenio II. In 1222 Pope Onorio III gave it to San Domenico for his Ordine and on that occasion the bell-tower and the nice cloister were built. Other restoration phases followed up, until the internal transformation by the hand of Domenico Fontana in 1587. During the two years of the world wars one proceded with the total recovery of the church, to the extent that it actually represents the most perfect type of Christian basilica from C.V. The façade, preceded by the atrium, consist of arcades supported by four antique marble columns fluted into spirals and four granite ones, which hold slabs’ fragments, sarcophagi from the Imperial age and ruins of antique barriers. The middel portal of the church, which has a nice Classical marble frame, is closed by precious wings made of cypress wood, reproducing scenes from the Antico and the Nuovo Testamento in relief. The interior, basilical, bright, wide and solemn, is divided up by three naves by twentyfour corinthian fluted columns. From the original decoration dated C. V one only finds a big mosaic strip with an inscription with nice golden letters on a light blue background, which bears the names of Pietro di Illiria and the Pope of that time, Celestino I. It is the only church that had the priviledge to own a baptismal spring.