Standing tall on a hill of the same name south of Argostoli, the Castle of St. George dominates Kefalonia's southwestern region. Its story begins with a Byzantine fort built on the summit, where a church dedicated to St. George once stood.

For three centuries (1185-1435), western rulers controlled the island and expanded the Byzantine fort, using it as a center for both administration and military operations.

The Turks briefly occupied the island twice (1479-1481 and 1485-1500), but the Venetians ultimately conquered the castle in 1500 after a grueling three-month siege that caused significant damage. Reconstruction began in 1504 and was completed by 1594.

The castle's perimeter walls stretch for 600 meters in an irregular shape, reinforced by three bastions. The most formidable one guards the castle's only gate, positioned strategically in the southeast.

A thriving settlement developed within the castle walls, eventually spilling outside to form the "Borgo" district. Here, the Church of the Evangelistria, a remarkable example of Ionian Baroque architecture, still stands.

The Venetian administration relocated to Argostoli in 1757, leading to the castle's gradual decline and eventual abandonment. Further damage came during World War II, inflicted by the British Protectorate, and the devastating earthquake of 1953.

Despite the damage, the Castle of St. George remains a significant work of fortification architecture, a powerful testament to Kefalonia's rich history.

Within the ruined walls, visitors can still find remnants of the Chapel of Panagia of the Guard, the Catholic Church of San Marco, the Church of San Nicolo, the house of the provveditore (governor), barracks, cisterns, warehouses, and a gunpowder magazine.