The vast basilica with an unfinished façade is in the typically unadorned Franciscan style. Inside, your eyes are soon drawn to the Cappella Bacci behind the altar, where Piero della Francesca left one of the finest examples of Tuscan Renaissance painting: frescoes illustrating the Legend of the True Cross. These ten scenes painted between 1452 and 1466 alone make a visit worthwhile. In addition, the church has a remarkable stained-glass window by Guillaume de Marcillat.