Nestled in the shadow of the huge Gothic church of San Francesco , this 15th-century oratory is dedicated to St Bernardino and decorated with Mannerist frescoes by Il Sodoma, Beccafumi and Pacchia. Upstairs, the small Museo Diocesano di Arte Sacra has some lovely paintings, including Madonna del Latte (Nursing Madonna, c 1340) by Ambrogio Lorenzetti.
