The fourteenth-century Franciscan church on the north side of Corso Rossellino, one of the few medieval buildings that survived Pius II's Renaissance demolition almost intact. The plain Gothic facade and single-nave interior feel a world away from the architectural ambition of the cathedral, fifty metres away.
The nave is decorated with fragments of fourteenth- and fifteenth-century frescoes — the cycle of the life of Saint Francis on the right wall is by an anonymous follower of Pietro Lorenzetti. The cloister behind the church is open during the day and a quiet place to sit when the piazza is crowded.