The collegiate church has very ancient origins and is the second for importance on the entire Diocese of Pescia. There is news of a church dedicated to the protomartyr Stefano for the first time in 1045, however some research led to suppose that ecclesiastical architecture was much older and perhaps aggregated to the Domus Regia, namely the political curia - administrative of the land of Pescia. The current architectural conformation follows the ancient structure; the apse of the ancient medieval church stood where today is the entrance and then the facade (to the west) was next to the bell tower. The interior has three naves and at the end three quadrangular apsids. In 1519, when the Church of Pescia was elevated to the rank of Diocese, this building was enlarged and transformed thanks to the intervention of important local families such as the Pagni, the Buonvicini, the Forts, the Sandri, the Snipers. Then stone altars were erected and masterpieces were commissioned to enrich the interiors: first of all the wooden group formed by the Announcing Angel and the Announced Virgin, both of the late fourteenth century near the school of Valdambrino. On the altar of the Sandri Family there is the canvas of the Visitation of Agostino Ciampelli of 1594. The valuable Liberation of St. Peter from prison, by the Bolognese Alessandro Tiarini is from the first years of the seventeenth century. On the left wall of the choir there is a paint on a plate with a gold background, of the second half of the fifteenth century, depicting the Madonna and Child and angels, while on the right one there is a Madonna and Child, attributable to the sixteenth century, with St John the Baptist and St Augustine. In the chapel of the SS Sacramento stands on the altar the canvas of Tobiolo that gives the view back to the father of Alessandro Bardelli, dating back to the early thirty years of the seventeenth century. There is also the wooden crucifix of the school of Andrea Pisano of the fourteenth century. In the second altar on the left (of the Buonvicini family) is preserved the canvas representing The Conversion of St Paul by Aurelio Lomi of the last years of the sixteenth century. In the sacristy of the canons are exhibited important canvases and benches of the seventeenth century. Also in this collegiate church there was the ancient brotherhood of Mercy, an institution founded in 1506 possessing many works of art including the extraordinary table representing Our Lady of the Mercy with women in prayer, attributable to a master of the sixteenth century Tuscan.