 Complete the following phrase:  After the naval victory at Cyzicus, the ancient Athenian general Alcibiades possibly built a custom station for ships coming from the Black Sea on a small rock in front of Chrysopolis todays Üsküdar. In 1110 Byzantine Emperor Alexius Comnenus built a wooden tower protected by a stone wall. From the tower an iron chain stretched across to another tower erected on the European shore, at the quarter of Mangana in Constantinople. The islet was then connected to the Asiatic shore through a defense wall, whose underwater remains are still visible. During the Ottoman 