The Cathedral, whose correct name is Collegiata di Santa Maria Assunta, is a 12th-century building, characterized by a Romanesque-style façade and divided into three naves. Inside, the Church houses numerous treasures: in fact, the walls of the Collegiate Church are richly decorated with frescoes and works (such as the Martyrdom of San Sebastiano by Benedetto Gozzoli and the Last Judgment by Taddeo di Bartolo), while inside the Dormitory dei Cappellani houses the Museum of Sacred Art. Piazza del Duomo, which houses the religious building, is the main square of the city - as it is natural to imagine -: it is the beating heart of the city. Surrounded by splendid buildings, it has always been the center of the village, as well as its religious and political nucleus.