In the narrowest part of the Bosphorus, the spot where Darius the Persian crossed in 500 B.C. with an army of 700,000 men on a pontoon bridge, Fatih built this defensive and offensive castle in 1452 to consolidate his control over the Straits. This castle is on impressive sight. There is an Arabic insicriptlon above the South Gate giving the dote and a .prayer for the great Fatih. Defense against a land attack is facilitated by the clever positioning of the three great towers, great exomples of medieval oriental military engineering, and the other One oblong, 6 polygonal, and 6 circular-towers. it is compared by Byzantine writers to the shape of a camel, by Europeans to a vast toy. The 5 gates are called the Mountain Gate, the Dizdar (guard) Gate, the Veii Gate, the Flood Gate and the Secret Gate. The northern tower is the Kara Kule (Black tower), the southern the GQi (Rose) Kule. They and the polygonal tower were designed to defend the gates and other towers. The former conical roofs and the wooden parts have not remained.
In the 16 th century Baron Wratislaw, who came bearing gifts frofn the Emperor Rudolf II for Murat ill, was imprisoned in the Black Tower, where his name may allegedly still be discerned where he scratched it on the wall. After many years he was freed by the intercession of the British Ambassador. His memoirs were published (Diary of an Embassy- Rev. A.H, Wratislaw).
South of the Castle below Bosphorus University is the Asiyan Museum where Jived and died the great poet Tevfik Fikret Aşıyan. it is dedicated to the New Literature Movement of which he was a leader.