THE GOLDEN HORN

ISTANBUL, TURKEY

The Byzantine Empire had its naval headquarters there, and walls were built along the shoreline to protect the city of Constantinople from naval attacks. 

At the entrance to the Golden Horn on the northern side, a large chain was pulled across from Constantinople to the old Tower of Galata to prevent unwanted ships from entering. 

Known among the Byzantines as the Megàlos Pyrgos (meaning "Great Tower" in Greek), this tower was largely destroyed by the Latin Crusaders during the Fourth Crusade in 1204.

In 1348, the Genoese built a new tower nearby which they called Christea Turris (Tower of Christ), now called Galata Tower.

--Wikipedia