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Istanbul (Turkey)

2500 Years on the Bosporus


Valens Aqueduct, Sultanahmet, Istanbul (built 373-400 AD)

Valens Aqueduct, Sultanahmet, Istanbul (built 373-400 AD)

David Veksler Golden Gate of the Theodosian Wall, Istanbul (412-414 AD)

Golden Gate of the Theodosian Wall, Istanbul (412-414 AD)

Verity Cridland Interior of the Hagia Sofia (Aya Sofya) Mosque, Istanbul

A general view inside the Haghia Sofia (Aya Sofya) on February 23, 2012 in Istanbul, Turkey.

Dan Kitwood / Getty Images News / Getty Images

The city of Istanbul, Turkey, is today the largest urban community in Europe, with a current population of some 25 million inhabitants. The city is located on a triangular peninsula created by the waters joining the Mediterranean and Black Seas and separating the continents of Europe and Asia, and it has excellent natural facilities for defense against military attacks.

Romans and Byzantines

Istanbul was founded as Byzantium (or Byzantion) in the mid-6th century BC, and for several centuries, it stayed a fairly small backwater in the Roman Empire. In 324 AD, the Roman ruler Constantine the Great remade the city into an Imperial capital, renamed it Constantinople, and increased the population from about 2,000 to 350,000. In 392, Theodosios I prohibited the performance of pagan rituals, and 45 years later, his descendent Theodosios II ordered the destruction of pagan temples and monuments. The process of Christianization of Constantinople had begun.


During the reign of Justinian (527-565), Constantinople's 500,000 people experienced a period of high prestige and cultural importance among the societies in Europe and Asia. Justinian extended the Byzantine empire to an area enclosed by the Danube southward to middle Egypt, and between the Rock of Gibraltar and the Euphrates River. Among his achievements such as several parks, a theatre in Galata and the Palace of Hormidas, Justinian built the Hagia Sophia, a tremendous architectural achievement created by the architects Isidore of Miletos and Anthemios of Tralles.

The Justinian empire fell apart shortly after his death, and by 750, Constantinople's population had dropped to 50,000, caused in part by the repetitive Justinian plagues, the expansion of the Islamic empire, and a transformation into a rural dispersed city.

Ottoman Empire

The empire had a revival between the 9th and 12th centuries; but Constantinople was captured during the Crusades in 1204, and it fell to the Ottoman empire under the direction of Mehmet I in 1453. Population estimates for Constantinople in the 18th century range between 400,000 and one million.

Constantinople was officially renamed Istanbul in 1923; and as a result of its long and varied history, today it retains some of the most beautiful architecture in the world.

Further Information on Istanbul

  • For more history of Constantine and his city, see N.S. Gill's article on Constantine the Great.
  • See Constantinople Under Constantine

Also Known As: Byzantium, Byzantion, Constantinople, Istanbul

Alternate Spellings: Konstantinoupolis (Greek spelling)

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