The first small church was built by Pope Gregory I, whose family had large estates in the area, around the beginning of the seventh century. Church was restored again in 1718 to designs by Giuseppe Sardi who transformed it from Romanesque to Rococo style and in 1899 by G.B. Giovenale who eliminated these elements to restore the church to its original Romanesque appearance that still preserves. The facade, hut-shaped, has a portico with seven arches. On the right stands Romanesque bell tower dating from the twelfth century, which rises seven floors with mullioned windows and colored tiles. The interior has three naves separated by pillars and eighteen columns of various origin. Wooden ceiling, consisting of trusses, while the floor is enriched by enamels and gold cosmateschi mosaics. You can admire the choir, in the middle of the nave, Chair, Gothic altar ciborium by Deodato Cosma, and the altar of red granite on the apse, dating back to 1123. On the left of the porch you can see famous Mouth of Truth and a reliquary containing St. Valentine's skull.