The Church of San Pietro has been one of the most important churches in the history of Grosseto. Also one of the terzieri (subdivisions of the town) and one of the gates of the medieval walls were dedicated to San Pietro. The Church is mentioned in documents of the XII, XIII and XIV century, but the excavations carried out in 2004 revealed that the Church could date back to a period between the end of the VIII century and the beginning of the IX century. Originally, the Church was smaller in size compared to the present Church, but it was certainly one of the first building made of stone in the castrum of Grosseto, which was built with wood and mud at that time. The Church in its current shape must have been erected immediately after the year 1138, when the Bishop’s Seat was transferred from Roselle to Grosseto. The Church, built with travertine, has pilaster strips and a Lombard band on its exterior surface. The façade features four bas-reliefs dating back to the period between the XII and XIII century, perhaps related to the Cathedral. Inside the Church, a crucifix of the late XIV century deriving from the Church of Santa Maria di Gancia.