Built around 1508 for Pandolfo Petrucci, called "il Magnifico", the de facto ruler of Siena at the turn of the 16th century. The façade carries some of the iron bronze ring-holders for which Sienese palaces are famous — used for tying horses, hanging lanterns, and flying contrada banners during the Palio.
The interior is not open to the public. The location, just below the Baptistery, makes it a natural pause between the cathedral complex and a walk down towards the Campo.