The fortified ensemble of Bellinzone is a unique example of European architecture erected in defence of the feudal structure guarding a key strategic Alpine pass. The Bellinzone ensemble is the sole remaining example in the entire Alpine region of medieval military architecture, comprising three castles, a wall that once closed off the whole Ticino valley, and the ramparts which surrounded the town for the protection of its citizens. Bellinzone owes its origins to its strategic position controlling access, via the Ticino valley, to the main Alpine passes into the Milanese, i.e. the whole north of Italy.
Recent excavations have shown that the site was inhabited as early as the Neolithic period. It was a Roman outpost until the frontiers of the empire were pushed further north to the Danube. Under pressure from barbarian inroads from the north, Bellinzone once again became a defensive stronghold against the peoples streaming down from the plains of central Europe. In the troubled days of the declining Roman Empire, the site fell into the hands of the Ostrogoths, the Byzantines, and finally the Lombards.
In the 10th century, Bellinzone formed part of the possessions of Otto I, founder of the Holy Roman Empire. The earliest constructions still extant probably date from around this period. Around the year 1000, the castle and the county were granted by the emperor to the Bishop of Como. It was at this period that the interior of the castle of Castelgrande was divided up to accommodate houses, turning it into a small fortified town. In the 12th century, Frederick Barbarossa took possession of the fortress. The town grew up gradually around the citadel and the fortifications were improved. Between the 13th and 15th centuries, the town expanded around the castle. The Castle of Montebello was built around 1300 and soon incorporated into the system of fortifications. The Castle of Sasso Corbaro built in 1480 to the south-east of Castelgrande.
Bellinzone became part of the state of Milan under the rule of the Visconti, who strengthened its defences considerably and began the construction of a wall running from Castelgrande to block the Ticino valley: the wall was known as the Murata.
At the beginning of the 16th century, Bellinzone fell to the confederates, and the fortifications lost much of their importance but were not destroyed. In 1803, Castelgrande was used as prison and an arsenal. The modern town developed at the expense of the ramparts. In 1882, the arsenal was extended. In the 20th century the major restoration work began. The ensemble of three castles and a network of fortifications are: Castelgrande (Château d'Uri, Château Saint-Michel), Château de Montebello (Château de Schwyz, Château Saint-Martin); and Château de Sasso Corbaro (Château d'Unterwald, Château Sainte-Barbara).
The Castelgrande is the largest of the three fortresses and dominates the town from its rocky eminence with its two towers, known as the White and Black Towers respectively. The spacious interior is divided by internal walls radiating out from the Black Tower into three courtyards. The White Tower, to the east, is surrounded by its own set of fortifications, known as the Redoubt. The arsenal consists of a series of massive buildings on the western side of the south courtyard. The enceinte has two chapels, but only their foundations still survive. Montebello Castle lies on a rocky spur to the east of Castelgrande, with which it is linked by the town walls; unlike Castelgrande, it is surrounded by deep moats. Its core is the central keep, from the end of the 13th century, which was given additional protection in the form of new defensive walls in the mid-14th and late 15th centuries. Sasso Corbaro Castle does not form part of the defensive perimeter of Bellinzone: it covers a vulnerable approach route. It is square in plan, the keep jutting out on the north-eastern corner and rising slightly above the level of the crenellated walls. Some two-thirds of the original line of the Town Ramparts still survive, with interval towers, but the gates have disappeared.