Kelefa Castle, Ottoman fortress built in 1679 at a strategic location above the Bay of Oitylo in the Mani peninsular, Greece. The castle was the seat of Hassan Pasha and was maintained by the Turks until 1685 when the Venetians and their Mani allies conquered it. The Venetians perfected it and made it one of their strongest castles. In 1715, it was handed back to the Turks by treaty but was gradually abandoned. The castle covered 13 acres and had relatively thin walls but four impressive circular towers. There was also a fifth one, which was demolished. The southern circular tower is the only one that survives in good condition. The Republic of Venice was a maritime empire and consisted of a congeries of colonies along the Adriatic and into the eastern Mediterranean, and acquired Kelefa to protect the all-important trade with Constantinople and the East.