It forms a deep natural harbor for the pensinsula it encloses together with the Sea of Marmara. 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 Horn, there was a large chain pulled across from Constantinople to the old Tower of Galata (which was known as the Megalos Pyrgos (Great Tower) among the Byzantines) on the northern side, preventing unwanted ships from entering. This tower was largely destroyed by the Latin Crusaders during theFourth Crusade (1204), but the Geneose built a new tower nearby, the famous Galata Tower (1348) which they called Christea Turris (Tower of Christ).
Istanbul (historically Byzantium and later Constantinople; see the other names of Istanbul) is the largest city of Turkey and the third largest city in the world. The city covers 27 districts of the Istanbul province.It is located on the Bosphorus Strait and encompasses the natural harbor known as the Golden Horn, in the northwest of the country. It extends both on the European (Thrace) and on the Asian (Anatolia) side of the Bosphorus, and is thereby the only metropolis in the world which is situated on two continents. In its long history, Istanbul served as the capital city of the Roman Empire (330–395), the East Roman (Byzantine) Empire (395–1204 and 1261–1453), the Latin Empire (1204–1261), and the Ottoman Empire (1453–1922). The city was chosen as joint European Capital of Culture for 2010. The historic areas of Istanbul were added to the UNESCO World Heritage List in 1985.