The Church of San Silvestro in Proh, dedicated to the famous 4th-century pope (it once housed some of his relics), has very ancient origins: it served as the military chapel of the Biandrate Counts, first mentioned in 1084, and formed part of an 11th-century fortified complex, which no longer exists, though its ruins are still visible near the building. It served as a parish church during the episcopate of Litifredo in the mid-12th century.
It survived the destruction of the castrum, which occurred following the conflict between the Visconti and the Paleologi of Monferrato in 1358–63, and served as the historic parish church of the community of Proh.
The building, comprising a single nave and featuring a gabled façade, houses important frescoes dating from the late 15th to early 16th centuries, painted in the wake of the plagues that regularly struck local communities during those years: these include a triptych depicting Saints Roch, Fabian and Sebastian; a Virgin and Child, enthroned; and a Saint Liberata, the patron saint of twin births and newborns following the pandemic.
There is also a Last Judgement depicted on the inner façade of the bell tower, which was once open and visible as one ascended the staircase. Despite centuries of alterations that have changed its original layout, the church remains a valuable testament to the ancient village of Proh and to the popular devotion associated with the feudal lords of the area. In 2024, it was saved from certain collapse thanks to a conservation restoration project by the UniversiCà Foundation, which also manages the nearby Castle.