Situated atop a hill in Upper Maremma, the Castle of Montemassi is an important architectural structure in the province of Grosseto. At present, the residence of the lords governing the area, a water tank next to the palace and the ruins of a square-based tower are still to be admired.

According to documents dating back to the 11th century, in 1076 the castle belonged to a certain count Ildebrando, whereas in the 13th century it belonged to the Aldobrandeschi family. In 1260, the castle was completely destroyed after a siege.

After having passed in the hands of count Pannocchieschi in 1306, in 1328 the castle, supported by Castruccio Castracani degli Antelminelli, rose up against Siena but the Sienese army repressed the riots. This historical event is celebrated in the famous fresco "Guidoriccio da Fogliano at the Siege of Montemassi", by Simone Martini, decorating the Palazzo Pubblico in Siena. The Republic of Siena assigned then the signory over the castle to the Salimbeni family. In 1375, the castle rebelled for the second time and the Salimbeni lost their signory.

The castle was then sold to Mino Verdelli, who maintained it for seven years. After having resumed the property of the castle, in 1404 the Republic of Siena decided to dismantle it in order to avoid further riots.

In 1632, Ferdinand II Grand Duke of Tuscany assigned the castle to the Malaspina family, who sold it to the marquis Domenico Cambiasoin 1770. In the following centuries, the castle has experienced a long period of decadence.