Bellinzona has always occupied an important geographic location in the Swiss Alps.
It is situated a few kilometres south of Arbedo, where the Ticino and Moesa meet.
Several key Alpine pass routes, connecting northern to southern Europe, including the Nufenen, St. Gotthard, Lukmanier and San Bernardino, all converge in the area around Bellinzona making it a key trading center.

While the region has been occupied since the early Neolithic age 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.
 While the fort fell into disrepair in the following centuries, it was rebuilt and greatly expanded in the 4th century AD.
 During the reign of Diocletian and Constantin 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.
 This castle, which was capable of holding a cohort — several hundred men — was tested in 475 when a formation of 900 Alemannic soldiers was defeated by the smaller castle garrison.
 
Following the collapse of the Western Roman Empire the successor states, which included the Ostrogoths around AD 500, the eastern Byzantine Empire towards the middle of the 6th century, and the Longobards from 568/70, all took control of Bellinzona and used the Castelgrande castle to assert control of the surrounding passes.
 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.
 According to legend, a spear thrust from a defender killed the attacking commander and ended the invasion.
 From Bellinzona the Longobards controlled the traffic on the important trade route from Varese over Ponte Tresa, the Monte Ceneri Pass, Biasca and finally over the Lukmanier Pass into Chur.
 Some researchers believe that Bellinzona may have been the capital of a county that included most of the valleys in Ticino.
 
At around 774 the Frankish Kingdom (that would become the Carolingian Empire) gained control of the Ticino valley including Bellinzona.
 Castelgrande was expanded with a chapel, apartments, towers and barracks.
 Older buildings and walls were rebuilt and strengthened.
 However, the southern part of the castle was destroyed by what appears to be an accidental fire in about 800AD.
Bellinzona has always occupied an important geographic location in the Swiss Alps. It is situated a few kilometres south of Arbedo, where the Ticino and Moesa meet. Several key Alpine pass routes, connecting northern to southern Europe, including the Nufenen, St. Gotthard, Lukmanier and San Bernardino, all converge in the area around Bellinzona making it a key trading center.
While the region has been occupied since the early Neolithic age 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.  While the fort fell into disrepair in the following centuries, it was rebuilt and greatly expanded in the 4th century AD.  During the reign of Diocletian and Constantin 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.  This castle, which was capable of holding a cohort — several hundred men — was tested in 475 when a formation of 900 Alemannic soldiers was defeated by the smaller castle garrison.  
Following the collapse of the Western Roman Empire the successor states, which included the Ostrogoths around AD 500, the eastern Byzantine Empire towards the middle of the 6th century, and the Longobards from 568/70, all took control of Bellinzona and used the Castelgrande castle to assert control of the surrounding passes.  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.  According to legend, a spear thrust from a defender killed the attacking commander and ended the invasion.  From Bellinzona the Longobards controlled the traffic on the important trade route from Varese over Ponte Tresa, the Monte Ceneri Pass, Biasca and finally over the Lukmanier Pass into Chur.  Some researchers believe that Bellinzona may have been the capital of a county that included most of the valleys in Ticino.  
At around 774 the Frankish Kingdom (that would become the Carolingian Empire) gained control of the Ticino valley including Bellinzona.  Castelgrande was expanded with a chapel, apartments, towers and barracks.  Older buildings and walls were rebuilt and strengthened.  However, the southern part of the castle was destroyed by what appears to be an accidental fire in about 800AD.
Castles of Bellinzona