The Hagia Sophia (532 - 537 A.D.) Istanbul, Turkey

The Hagia Sophia was erected during the reign of Emperor Justinian (532 - 537 A.D.), when the Byzantine Empire was at the height of its power and influence. The massive dome, which is the prominent architectural feature, has since often been used as a model for the design of Islamic mosques. Indeed, after the fall of Byzantium, the Hagia Sophia was converted into an Ottoman mosque. Today, the monument is a museum serving both Christians and Muslims.