Rumelihisarı (Rumelian Castle) is a fortress located in the Sarıyer district of Istanbul, Turkey, on a hill at the European side of the Bosporus. It gives the name of the quarter around it. It was built by the Ottoman Sultan Mehmed II between 1451 and 1452, before he conquered Constantinople. The three great towers were named after three of Mehmed II's viziers, Sadrazam Çandarlı Halil Pasha, who built the big tower next to the gate, Zağanos Pasha, who built the south tower, and Sarıca Pasha, who built the north tower.
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.