 The most densely populated areas tend to lie to the northwest, west, and southwest of the city center, on the European side; the most densely populated district on the Asian side is Üsküdar.Istanbul has been a cosmopolitan city throughout much of its history, but it has become more homogenized since the end of the Ottoman Empire.The vast majority of people across Turkey, and in Istanbul, are Muslim, and more specifically members of the Sunni branch of Islam.