Istanbul is Turkey's most populous city as well as its cultural and financial hub. Located on both sides of the Bosphorus, the narrow strait between the Black Sea and the Marmara Sea, Istanbul bridges Asia and Europe both physically and culturally. Istanbul's population is estimated to be between 12 and 19 million people, making it also one of the largest cities in Europe and the world.
With its long history at the center of empires, Istanbul offers a wealth of historic and religious places to take in. The bulk of these ancient monuments, dating back to Roman, Byzantine, and Ottoman periods, including the Hagia Sophia, Topkapı Palace, Sultan Ahmet Mosque (Blue Mosque), and Basilica Cistern are located around Sultan Ahmet Square, while some others are dispersed throughout the peninsula of old city, such as Church of St Savior in Chora (Kariye Müzesi), entire inside of which is covered by mind-blowing frescoes and mosaics. An impressive section of mostly intact Theodosian walls, which mark the full length of western boundary of the peninsula, is right next to this particular church.
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