The Palazzo Piccolomini is a good example of a Renaissance-style private residence. It was started in 1469 for the relatives of Pope Pius II, a member of the Piccolomini family.

Today it houses the State Archives and, in addition to documents relating to the history, the organisation and the administration of the Republic of Sienna, it holds the exceptionally interesting collection of the "Tavolette di Biccherna", painted wooden tablets which were used to cover the Republic's financial books.
These small paintings are of great value and some of them are works of such Sienese painters as Pietro and Ambrogio Lorenzetti, Giovanni di Paolo, il Vecchietta and Francesco di Giorgio Martini.

The nearby Logge del Papa was constructed in 1462 by Pope Pius II. Designed by Antonio Federighi, the style is Renaissance with three expansive, majestic arches forming the colonnade. The monumental severity of this building is typical of this district in Sienna's historical center.