Corfu. It was an acropolis which surveyed the region all the way to the southern Adriatic and presented a formidable strategic vantage point to the occupant of the castle. Angelokastro formed a defensive triangle with the castles of Gardiki and Kassiopi, which covered Corfu's defences to the south, northwest and northeast. The castle never fell, despite frequent sieges and attempts at conquering it through the centuries, and played a decisive role in defending the island against pirate incursions and during three sieges of Corfu by the Ottomans, significantly contributing to their defeat. During invasions it helped shelter the local peasant population. The villagers also fought against the invaders playing an active role in the defence of the castle. Angelokastro, located at the western frontier of the Empire, was instrumental in repulsing the Ottomans during the first great siege of Corfu in 1537, in the siege of 1571 and the second great siege of Corfu in 1716 causing the Ottomans to fail at penetrating the defences of Corfu in the North. Consequently the Turks were never able to create a beachhead and to occupy the island. Gardiki Castle Gardiki Castle () is a 13th-century Byzantine castle on the southwestern coast of Corfu and the only surviving medieval fortress on the southern part of the island. It was built by a ruler of the Despotate of Epirus, and was one of three castles which defended the island before the Venetian era (1401–1797). The location of Gardiki at the narrow southwest flank of Corfu provided protection to the fields and the southern lowlands of Corfu and in combination with Kassiopi Castle on the northeastern coast of the island and Byzantine Angelokastro protecting the northwestern shore of Corfu, formed a triangular line of defence which protected Corfu during the pre-Venetian era. Kassiopi Castle Kassiopi Castle () is a castle on the northeastern coast of Corfu overseeing the fishing village of Kassiopi. It was one of three Byzantine-period castles that defended the island before the Venetian era (1386–1797). The castles formed a defensive triangle, with Gardiki guarding the island's south, Kassiopi the northeast and Angelokastro the northwest. Its position at the northeastern coast of Corfu overseeing the Corfu Channel that separates the island from the mainland gave the castle an important vantage point and an elevated strategic significance. Kassiopi Castle is considered one of the most imposing architectural remains in the Ionian Islands, along with