Built on the site where Bernardino of Siena, the great 15th-century preacher, used to address open-air crowds in Piazza San Francesco. The upper oratory holds an extraordinary fresco cycle of the Life of the Virgin by Sodoma, Beccafumi, and Girolamo del Pacchia — a compact survey of mature Sienese Renaissance painting.
The hours are limited and visits usually require a small group; tickets are sold together with the Museo Diocesano next door. Check current opening with the cathedral ticket office.