93% of population in Turkey is Muslim. Since 10th century, Islam have become the most practiced religion in Anatolia. Anatolia means Turkey today. Most of Muslims in Turkey are Sunnis. Also There are some Alawites in Muslim community. Also %5 Christian and %2 Jews living in Turkey.
Istanbul had been the final seat of the Islamic Caliphate, from 1517 to 1924. Ottoman Sultan Bayazıd had brought and preserved some relics of prophet Muhammad, Abraham, and King David in Topkapi Palace, Eyup Sultan Mosque and several other prominent mosques of Istanbul for hundreds of years.
After the collapsing of Ottoman Empire, Mustafa Kemal Ataturk had founded the Turkish Republic. The secularization had started in the society with the foundation of new country. Also It was the most prominent and controversial feature of Ataturk’s reforms. Under the leadership of Ataturk had abolished the caliphate with his leadership. He had eliminated and reduced the power of Islamic religious authorities.
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. Conqueror Fatih Sultan Mehmed had built the first mosque on Europan side of Istanbul in Rumeli Fortress 1452. Holy Apostles Church was the patriarch of Byzantine Empire. So They had built first imperial mosque over this church in 1470. It was very important Byzantine church and originally had been built during the Constantine the Great.
Architect Sinan had built many imperial Mosques during 16th century. He had built Suleymaniye Mosque for honor of Great Suleyman the Magnificent in 1557. And of course famous Sultan Ahmet Mosque (1616), “Blue Mosque” have become the imperial mosque of 17th century It has become very famous with finest very beautiful blue quartz tiles of 17th century.