Dating back to the early 860s, Aldobrandesco Castle was built by the Aldobrandeschi family on pre-existing buildings from the Lombard period. It is the oldest suburban government building in Italy and one of the oldest in Europe. In building the towers and the two crenellated walls between 970 and 995 AD, The Aldobrandeschi increased the height of the building by two floors, probably at the behest of Marquis Ugo of Tuscany. The castle underwent its most recent intervention in 1331 during the Sienese domination of the area under Guidoriccio of Fogliano and, in the second half of the 16th century, it became part of the Grand Duchy of Tuscany. According to some scholars, Aldobrandesco Castle is depicted in a fresco by Simone Martini in the Palazzo Pubblico in Siena.