The Church of St. Catherine of Alexandria was probably built during the second half of the 15th century within an ancient Roman construction, of which several blind arches in black flint opus reticulatum (reticulated work) still remain.
The Church houses a deteriorated 16th century fresco, a 17th century polychrome statue of St. Anthony Abbot and the tomb of Abbot Tommaso Silvestri, educator of the deaf and dumb and inventor of the phonic method. The two side chapels, dedicated to St. Anthony Abbot (on the east side) and St. Bernardino and St. Rita (facing), were added in 1620.
The pre-existing reticulated work brick structure shows signs of having been intentionally damanged to allow for the insertion of the portal and the two square windows. Fragments of this kind of wall covering, characterised in the lower part by a blind arcade, are visible along both the west side, where the arching appear to rise from the south to the north, and the northern side. In both case, the wall surface has been preserved mostly in the lower section of the parts of the walls that have not been subject to later additions, such as the Chapel of St. Anthony Abbot and the apse.
The remains of another entrance to the building can be seen low on the wall, close to the further chapel. It appears to have been filled in at a later date and was probably part of the oldest phase of the reticulated work construction. It does, in fact, go underground for more than a metre. It is probably the rectangular portal of the original, pre-15th century construction The original façade, therefore, would have faced West, in contrast to the later church of St. Catherine. The orginal floor was also lower than the present, modern one.
It is likely that the original constrution to which the reticulated work walls belong was a typical Romanesque church with a basilica floor plan of a nave and two aisles and a blind arcade decorating the exterior façade and flanks. There are decorative and, perhaps also planimetrical, elements reminiscent of the Pisano Romanesque style which can be found in the surrounding territory, and in the areas around Tuscia, Siena and Volterra. Using the typical façade – side ratio of 1:1.5 and starting from the 12 m façade, we can hypothesize that the church would have measured 18m in length (extending east). The blind arcade on the façade which grow progressively taller at the ends is the most obvious sign of an example of 12th century Siennese style (for example, the admittedly more refined façades of Pieve di St. Peter in Villore in S. Giovanni d'Asso, Pieve di S. Giovanni Battista in Corsano and Pieve di Pomarance.)