The Old Fortress can be seen from the Liston and was built here to protect the town from invasions from sea. It is thought the earliest fortifications on the site date from the 6th century after the Gothic invasion and the medieval town of Corfu developed within the boundaries of the peninsula. In the early 15th century the Venetians started replacing the old Byzantine fortifications.
The fort successfully repulsed three major Ottoman sieges, the great siege of 1537, the siege of 1571 and the second great siege of Corfu in 1716. Following the siege in 1537 the Venetian Governor ordered the construction of new bastions and towers which still exist today. They were designed by two Venetian military engineers Savorgnan and Martinengo and were considered masterpieces of military engineering.
To further strengthen the defences the moat was added by the Venetians and is called Contrafossa, access to the fortress was by a drawbridge but has now been replaced with a permanent structure. The two twin peaks within the castle are called Castel a Terra and Castel a Mare and are visible just above the Contrafossa, both peaks were fortified by strong towers.
The Castel da Mare peak housed the powder magazine and was struck by lightning in 1718. The explosion destroyed three secondary ammunition facilities and also destroyed most of the buildings inside the castle including the palace of the Captain General.
Both the old and new fortresses had Governors who were elected by the Venetian senate and were appointed for a period of two years. As part of their oath to the senate they had to agree not to communicate with each other in order to ensure neither would persuade the other to commit treason against the republic.
During World War Two the Fortress was used by the Nazis to imprison Jews prior to their deportation. On 8 June 1944 the Jews of Corfu were told to be present at the fortress, some hid in the hills but most turned up as ordered. They were then imprisoned in harsh conditions with no facilities before they were transported across Europe to the Birkenau camp. Of the 1,800 Corfiot Jews who were deported 120 eventually returned after the war.
Today the Fortress houses the Public library of Corfu which is located in the old British barracks and also plays host to various exhibitions and concerts, there is also a Café within the grounds.