The history of Assos revolves almost exclusively around its imposing castle. Its construction began by the Venetians in the late 16th century (1593), with an ambitious vision: to become the new capital of Kefalonia and a strong fortress against pirate raids. Indeed, for many years it served as the seat of the Venetian Provveditore (Governor) of the northern side of the island. Although it was one of the largest castles in Greece, it was never densely populated. Its use changed dramatically after the unification of the Ionian Islands with Greece, when it was converted into an agricultural prison for many decades. Its final abandonment came after the devastating earthquakes of 1953, when its last residents left. Today, although it remains in ruins, one can admire the well-preserved vaulted entrance, parts of the walls, and various buildings, such as the church of Prophet Elias.