The urban landscape of the city has been shaped by many communities. The most popular major religion is Islam. The first mosque had been built in Kadikoy on the Asian side of the city which had been conquered by the Ottomans in 1353. The first mosque on the European side had been built inside the European Fortress in 1452 while building up fortress. The first imperial mosque was the Fatih Mosque (1470) which had been built up near the Church of the Holy Apostles. It was very important Byzantine church and originally had been built up during the Constantine the Great. Some other imperial Mosques had been built up during the following centuries like Suleymaniye Mosque (1557) which had been built up for honor of Great Suleyman the Magnificent by great Architect Sinan, and of course famous Sultan Ahmet Mosque (1616), has been also known as “Blue Mosque” because of very beautiful blue quartz tiles of 17th century which adorn its interior.
Istanbul had been the final seat of the Islamic Caliphate, from 1517 to 1924. Some of the personal belongings of prophet Muhammad, Abraham, David and the earliest caliphs who followed Muhammad have been preserved in Topkapi Palace, Eyup Sultan Mosque and several other prominent mosques of Istanbul for hundreds of years.