Hagia Sophia, Istanbul

Istanbul, formerly Constantinople, lies on both sides of the Bosporus Strait, which separates Europe and Asia. On the western bank lies Hagia Sophia, built between 532 and 537 A.D. during the reign of the Byzantine emperor Justinian. The basilica is crowned by a majestic cupola more than 98 feet (30 m) in diameter and rising 184 feet (56 m) in the air, a technical marvel at the time. After Constantinople fell to the Turks in 1453, Hagia Sophia was transformed into a mosque, and four minarets were added to its initial structure. In 1934, on the order of the government of the nonsectarian Turkish Republic, it became a museum, and most of its magnificent Byzantine mosaics have been restored. Christian for nine centuries, Muslim for more than 500 years, Hagia Sophia illustrates the contrasting destiny of Istanbul, the only city in the world that is divided between two continents. Christianity has nearly 2 billion followers around the world, almost twice the figure for Islam, which has 1.2 billion followers. However, according to demographic forecasts, this proportion could be reversed by the end of the twenty-first century.