The main approach of the Ottoman Empire is to grab the Constantinople and the Islam culture to create an Islamic Roman Empire. In this period, the attitude of the Byzantine architecture and also art have diversified the Damascus, Kiev, Venice, and Cordoba. And then finally Fatih Sultan Mehmet have successfully conquered the Constantinople in 1453. Fatih Sultan Mehmet changed the name of Constantinople into İstanbul. And then for the different ethnic groups in İstanbul governed by the new new laws of owned by him. Also, in order to encourage the merchant activities, he constructed Kapalı Çarşı as Seljuk has approached as well in Koza Han consisted of square bays capped with rounded. Fatih has inspired by the Italy’s technical and cultural innovations, especially the city walls of the new city. They constructed fortifications on the Bosporus to block the Christian naval support to Byzantine. These Yedikule fortifications were star shaped. He converted Hagia Sophia into the Palantine church, added minarets to make a royal church and also changed the main axis. And then on, he constructed Fatih Camii with the inspiration that he gathered from great Byzantine church. This new church was rival with the Hagia Sophia. Because the grand hemispherical dome that is less than few meters diameter than Hagia Sophia. The small cubes were supported by pointed arches of old granite columns on top of each bays of the courtrooms. Plus, he built a tube which is octagonal for himself and for mother of his heir. He demanded to add a brand new palace in the peninsula unlike the old palace in the center of the city. This new palace is called Topkapı Sarayı. It was like an antithesis of European palaces as asymmetrical and looking more like a garden rather than a building. The most significant parts of these palaces were divans and harems. Divan is mostly used for the official meetings of the government. It consisted of three domed spaces and L shaped.