The Patras Fortress (Greek: Κάστρο Πατρών) was built around the mid-6th century above the ruins of the ancient acropolis, on a low outlying hill of the Panachaiko Mountain and ca. 800 m from the sea. The castle covers 22,725 m² and consists of a triangular outer wall, strengthened by towers and gates and further protected originally by a moat, and an inner compound on the northeastern corner, also protected by a moat.

source: Wikipedia