This fullday tour of Istanbul visits sites in the historic area of Istanbul. - Hagia Sophia an important Byzantine structure in Istanbul and one of the world’s great monuments. - Sultanahmet Mosque is known as the Blue Mosque because of blue tiles surrounding the walls of interior design. (Closed on Friday) - The Topkapi Palace once served as the main residence and administrative headquarters of the powerful sultans of the Ottoman Empire during. (Closed on Tuesday) - Hippodrome of Constantinople, located in Sultanahmet/Istanbul, was a public arena mainly for chariot races.- Hippodrome - The Grand Bazaar built in the 15th century, is the oldest covered market in the world. (Closed on Sunday)