Castell'Azzara, a small town in the province of Grosseto and set at 815 m of altitude, was born from a medieval fortress dating to the XIII century, at least. The Convento della Trinità, founded in the XVI century, can be admired inside the town.

According to tradition, Ildebrandino, Bonifacio and Guglielmo Aldobrandeschi decided to build one of their strongholds on the Mount Penna after they had stopped here in 1212. This was the time when the Lombard-born family exercised its immense power on the territories of Grosseto and on the ancient estates belonging to the Abbey of San Salvatore. Then the territory was the target of the Republic of Siena and of Orvieto. The three brothers played dice for the ownership of the future fortress of Castell'Azzara.
Apart from this singular tale, the Aldobrandeschi had actually governed the area of Castell'Azzara since the XIII century. When this family divided into two branches, the area of Castell'Azzara was included into the properties of the Santa Fiora branch. For all the XIV century, many battles against the families of Orvieto, the Sienese and the Orsini family of Pitigliano were fought to get possession of the territory, until 1430.
In that year, the Aldobrandeschi family disappeared and the village passed to the Florentine family of the Sforza, who acquired it through marriage. In the XVII century, the territory that had belonged to the town of Santa Flora, was integrated in the Tuscan Grand Duchy dominated by the Medici. The mining industry linked to the caves of Castell'Azzara, started to grow little by little, and thanks to it the town's economy developed and its population increased, too, until the year 1015, when it obtained its autonomy. Today, Castell'Azzara has almost 1000 inhabitants.