The Castle of Mytilene (modern Mytilini), encompassing an area of 200,000 m2 (20 hectares), is considered one of the largest fortresses in the Mediterranean. Excavations by the Canadian Institute have uncovered the sanctuary of Demeter, proof that the site has been inhabited since antiquity. The first Byzantine phase of the fortress is estimated to date to the reign of Justinian (6th c. A.D.). The present form of the castle is the result of the building activity of the Gattelusi, who ruled the island during the Late Byzantine period (1355-1462), and above all the Ottomans, who occupied Lesbos from 1462 until 1912. It is divided into three parts in accordance with its overall configuration: the Upper, Middle, and Lower Castle.