The Castle of Mytilene, also Fortress of Mytilene, is located in Mytilene on the Greek island of Lesbos, North Aegean. It is maintained in good condition and is one of the largest castles in the Mediterranean covering an area of 60 acres. The first castle on the site may have been erected during the time of Justinian I (ruled 527–565). The 6th-century castle may have been built on top of an already existent fortress. In the late Middle ages, the castle was the residence of Francesco I Gattilusio and his successors, especially the tower known today as the Queen's Tower. There is also strong evidence that the original acropolis on the site may have included a sanctuary to Demeter, Kore and Cybele.