Grosseto () is a city and comune in the central Italian region of Tuscany, the capital of the Province of Grosseto. The city lies from the Tyrrhenian Sea, in the Maremma, at the centre of an alluvial plain on the Ombrone river. It is the most populous city in Maremma, with 82,284 inhabitants. The comune of Grosseto includes the frazioni of Marina di Grosseto, the largest one, Roselle, Principina a Mare, Principina Terra, Montepescali, Braccagni, Istia d'Ombrone, Batignano, Alberese and Rispescia. History The origins of Grosseto can be traced back to the High Middle Ages. It was first mentioned in 803 as a fief of the Counts Aldobrandeschi, in a document recording the assignment of the church of St. George to Ildebrando degli Aldobrandeschi, whose successors were counts of the Grossetana Mark until the end of the 12th century. Grosseto steadily grew in importance, owing to the decline of Rusellae and Vetulonia until it was one of the principal Tuscan cities. In 1137 the city was besieged by German troops, led by Duke Heinrich X of Bavaria, sent by the emperor Lothair III to reinstate his authority over the Aldobrandeschi. In the following year the bishopric of Roselle was transferred to Grosseto. In 1151 the citizens swore loyalty to the Republic of Siena, and in 1222 the Aldobrandeschi gave the Grossetani the right to have their own podestà, together with three councilors and consuls. In 1244 the city was reconquered by the Sienese, and its powers, together with all the Aldobrandeschi's imperial privileges, were transferred to Siena by order of the imperial vicar. Thereafter Grosseto shared the fortunes of Siena. It became an important stronghold, and the fortress (rocca), the walls and bastions can still to be seen. In 1266 and in 1355, Grosseto tried in vain to win freedom from the overlordship of Siena. While Guelph and Ghibelline parties struggled for control of that city, Umberto and Aldobrandino Aldobrandeschi tried to regain Grosseto for their family. The Sienese armies were, however, victorious, and in 1259 they named a podestà from their city. But Grosseto gained its freedom and in the following year and fought alongside the Florentine forces in the Battle of Montaperti. Over the next 80 years Grosseto was again occupied, ravaged, excommunicated by Pope Clement IV, besieged by emperor Louis IV and by the antipope Nicholas V in 1328, until it finally submitted to its more powerful