On the right bank of the small Göksu (Byz. Aretas) river, the Castle of Anatolia wos built in 1395 by Sultan Bayezit I Yildirim (Lightning) after his triumph at Nicopoiis. Like his grandson Mehmet II. Fatih, he was a great military commander, but, after successfully besieging Byzantium, he departed on the acceptance of his terms. These were that the keys of the city shouid be given him and a Turkish suburb with a Mosque be founded at Galata. Fatih later reinforced the castle when he built the similar Rumeli Hisarı, and the two of them closed the defence of the Straits.