This glorious city was the capital of the Byzantine Empire and later the Ottoman Empire; before it was Constantinople it was called Byzantium, and it has been officially known as Istanbul since 1930.
The Roman emperor Constantine moved the capital of his empire to Byzantium in 330 AD and renamed it Constantinople after himself. The location is a good one, for the city sits squarely between Asia and Europe with the sea on one side. To be defensible, the city was heavily fortified: Constantine had an inner wall built, and in the fifth century the construction of triple outer walls began. Inside the fortifications was a gorgeous city ranged on seven hills; there were many beautiful palaces and gilded domes and towers. Of particular note are the church of the Hagia Sophia, a huge hippodrome, and a Golden Gate which gave entrance to the city, but these were only the largest and most magnificent of the many public buildings and monuments that dotted this great city. Filled with great artistic and literary treasures, by the tenth century its cosmopolitan population numbered about a million people from all corners of Asia, Europe, and Africa.
Constantinople was beseiged many times and taken thrice: in 1204 by the army of the fourth Crusades; in 1261 by Michael VIII, and in 1453 by the Ottoman sultan Muhammad II. The first two saw many of Constantinople's treasures sacked and destroyed; the last caused a virtual depopulation. However, the city recovered each time, and the under the Ottoman empire it was further embellished with many impressive mosques, fountains, aqueducts, and other public edifices. After World War I the city was occupied by the Allies; the last sultan was deposed in 1922 and the capital of Turkey was moved to Ankara.