In piazza Gamurrini (formerly piazza Ialta), the Cassero owes its present look (Sienese depressed arches and scarp walls) to the reconstruction carried out by the Sienese when they became lords of Monte San Savino in 1383 and bought the Cassero from Deo di Guelfo Tolomei who had seized it. Then, Monte San Savino having fallen under the control of Florence in 1384, the lily of Florence was placed on the front of the fortress where it can still be seen. A moat encircled the stronghold and was crossed by a sturdy drawbridge at the main entrance. As time went by, the fortress lost its purpose and housed a pawnbroker (end of sixteenth century) then a poor home up to 1960.
Entirely renovated in the seventies, the Cassero is now the City Museum - displaying ceramic vessels and various works of art, among which is a carved and painted Sienese wooden Crucifix dating back to the fourteenth century – and Tourist Office. The premises are also used for temporary exhibitions and for public lectures.
The historical evidence, which point at Monte San Savino as a place of an old ceramics tradition are more and more significant. Monte San Savino is particularly specialized in pottery production of common use and taste. In the context of this production, which concerns the whole area of Valdichiana, the Monte San Savino production differs from others for its original models. Monte San Savino potters succeeded in proposing popular creations that recalled nobler pottery product.
The Town Museum recovers and preserves popular traditions. This has also been made possible thanks to the research studies carried out during cultural events on ceramics. The Museum also safeguards and reorganizes Valdichiana's popular ceramics and relevant documents and publications. The Museum is tied to the pottery workshop operative in the town in order to save the morphological and decorative examples of Monte San Savino's traditional production. In the museum, it is possible to admire Medieval and Renaissance findings such as a wonderful 14th century wooden Crucifix from the Senese school, recovered during the restoration of the Cassero, and archaic majolica works from the stronghold of Ciggiano.