Situated on the Alpine foothills, the group is composed of fortified walls and three castles named Castelgrande, Montebello and Sasso Corbaro.

Castelgrande is located on a rocky peak overlooking the valley, with a series of walls that protect the old city and connect to Montebello.

While the region has been occupied since the early Neolithic age[2] it was not until the late 1st century BC that a fort was built on the massive gneiss outcropping known as Castelgrande during the reign of the Roman Emperor Augustus.

During the reign of Diocletian and Constantine a chain of castles and watchtowers was built to protect northern Italy from invasion.

Bellinzona's location was recognized as a key point in the defenses and a large castle was built on the Castelgrande.

Under the Longobards, Bellinzona became the site of a permanent garrison to protect the region from raids by the neighboring Frankish and Alemannic tribes.

The historian, Gregory of Tours records that a Frankish invasion in 590 ended when it encountered heavy resistance from the Longobard defenders of the castle.

[4] At around 774 the Frankish Kingdom (that would become the Carolingian Empire) gained control of the Ticino valley including Bellinzona.

About two centuries later the Holy Roman Emperor Otto III, seeking to restore the power of glory of ancient Rome and expand into Italy, opened the Lukmanier and St. Bernard passes.

In 1002, following the death of Otto III, Marquis Arduino of Ivrea declared himself King of Italy and ratified the bishop's ownership of Castelgrande.

During the Investiture Controversy of the late 11th century the city of Bellinzona with its castle came under the control of the Hohenstaufens of Swabia.

However, in 1239, Como sided with the Emperor Frederick II who quickly moved forces into Bellinzona and strengthened Castelgrande.

In 1242 Milan sent Guelph (or pro-papacy) forces under the command of Simone di Orello to take Bellinzona.

[6] Pro-papacy Milan would dominate Bellinzona for the next one and a half centuries, though the pro-Imperial Rusca would also occupy part of the city.

[7] During the second half of the 14th century a long wall, known as the Murata, was built across the entire valley of the Ticino, of which the bottom is about one kilometre wide at Bellinzona.

During the period of unrest following Gian Galeazzo Visconti's death, a tower which would become the nucleus of the third castle, Sasso Corbaro, was built outside the city.

While they were unable to take Bellinzona, the victories of the Swiss troops led to Milan granting all of the Leventina Valley to Pollegio to Uri in 1441.

Following the death of Duke Filippo Maria Visconti in 1447, Bellinzona was in the middle of the succession crisis between Franchino Rusca of Locarno and Heinrich of Val Mesolcina, who were allied with Uri and the Ambrosian Republic in Milan.

The war following the succession crisis lasted nearly three years until Francesco I Sforza seized power in Milan.

Bellinzona would remain under the joint administration of Uri, Schwyz and Unterwalden until the creation of the Helvetic Republic after the French invasion of Switzerland in 1798.

[9] Following the Act of Mediation in 1803 Bellinzona became part of the independent canton of Ticino, and the castles became the property of the state.

In 1850 the new Federal Government, concerned over instability in neighboring countries, built a number of defensive fortification along the St. Gotthard pass.

The open space was divided into three large baileys which served to provide temporary housing for troops that could be stationed in Bellinzona.

The nearby South Wing, which marks the southern boundary of the castle, was built in two stages during the 13th and 15th centuries on the foundations of an earlier building.

The south wing houses a museum that contains "6500 years of human presence on the hill ... and covers the period from the first Neolithic village to the 20th century".

[13] The museum also includes the decorated ceilings of Casa Ghiringhelli and from a former inn, the Albergo della Cervia as well as a collection from Bellinzona's mint.

It was built before 1313 for the pro-Imperial Rusca family, who occupied the castle following the Visconti victory and occupation of Castelgrande.

The original entrance is located high on the western wall and can only be reached by climbing an external flight of stairs.

A little chapel, dedicated to Saint Michael, leans against the wall of the more recent south-facing section; built around 1600, it is one of the few buildings erected in the castles of Bellinzona under the rule of the three Swiss cantons.

Originally located in the entrance hall of their home in Olivone in the Blenio Valley, the room was purchased by the Canton of Ticino in 1944 and housed first in Castelgrande before being moved to the Sasso Corbaro in 1989.