The abbey of San Faustino was edified on the remains of a Roman villa. Recent excavations have digged out its foundations and some rooms that were used for storing agricultural products. The church is named after St Faustino who, according to the legend, was disciple of the bishop of Civitas Martana, St Felix. Around the 8th century the Benedictines edified, on the saint's tomb, the church and the nearby monastery. These are mentioned as subordinate of the monastery of Farfa in several documents dated 1115 and 1118. Afterwards the church was converted into collegiate church for the secular clergy.
The façade, in the Lombard style but spoiled by a modern porch (1950), has an elegant mullioned window with three lights and marble small columns. Next to the window are, on the right side, an epigraph with the inscription of Lucius Julius Marcianus and his wife Publicia; on the left side, a fragment of Doric friezewith small roses and bucranes metopes. Another fragment of the same frieze, which was embeded in a wall under a court window, has been recently moved inside the church.
The right side of the church is built on a high base made of travertin blocks; several semicircular pillars line it at regular intervals. Also the 13th century apse is semicircular in shape.
The aisleless inside, has been much reworked. It might have originally had a raised presbytery with underlying crypt. In the middle of the apse are, buried, two sarcophagi, one of them is venerated as St Faustino's. There are also several sculptural fragments from different time periods and several inscriptions. Among them very interesting is the one which mentions the call from Pope Pio II in December 1462.
Inside is a fresco by the painter Sebastiano Florii da Arezzo, which portrays the Madonna of Rosary (1580). Worth noting are the simple and rustic structure of the rooms of the ex-Benedictine monastery and an early Middle Age architrave on which are rough engravings of doubtful meaning.
The elegant bell tower is a recent construction (1925); it harmonizes well, however, with the Romanesque style of the church.