Constantinople: Capital of the Eastern Roman Empire

Domes of Hagia Sophia on foreground and Blue Mosque on foreground, Istanbul, Turkey
Alexander Spatari / Getty Images

In the 7th century BCE, the city of Byzantium was built on the European side of the Strait of Bosporus in what is now modern Turkey. Hundreds of years later, the Roman emperor Constantine renamed it Nova Roma (New Rome). The city later became Constantinople, in honor of its Roman founder; it was renamed Istanbul by the Turks during the 20th century.


Constantinople is located on the Bosporus River, meaning that it lies on the boundary between Asia and Europe. Surrounded by water, it was easily accessible to other parts of the Roman Empire via the Mediterranean, Black Sea, Danube River, and Dnieper River. Constantinople was also accessible via land routes to Turkestan, India, Antioch, the Silk Road, and Alexandria. Like Rome, the city claims 7 hills, a rocky terrain that had limited earlier utilization of a site so important for sea trade.

History of Constantinople

Emperor Diocletian ruled the Roman Empire from 284 to 305 CE. He chose to split the huge empire into n eastern and western parts, with a ruler for each portion of the empire. Diocletian ruled the east, while Constantine rose to power in the west. In 312 CE, Constantine challenged the rule of the eastern empire, and, upon winning the Battle of Milvian Bridge, became sole emperor of a reunited Rome.

Constantine chose the city of Byzantium for his Nova Roma. It was located near the center of the reunited Empire, was surrounded by water, and had a good harbor. This meant it was easy to reach, fortify, and defend. Constantine put a great deal of money and effort into turning his new capital into a great city. He added broad streets, meeting halls, a hippodrome, and a complex water supply and storage system.

Constantinople remained a major political and cultural center during the reign of Justinian, becoming the first great Christian city. It went through a number of political and military upheavals, becoming the capital of the Ottoman Empire and, later, the capital of modern Turkey (under the new name Istanbul).

Natural and Man-Made Fortifications

Constantine, the early fourth-century emperor known for encouraging Christianity in the Roman Empire, enlarged the earlier city of Byzantium, in CE 328. He put up a defensive wall (1-1/2 miles east of where the Theodosian walls would be), along the westward limits of the city. The other side of the city had natural defenses. Constantine then inaugurated the city as his capital in 330.

Constantinople is almost surrounded by water, except on its side facing Europe where walls were built. The city was built on a promontory projecting into the Bosphorus (Bosporus), which is the strait between the Sea of Marmara (Propontis) and the Black Sea (Pontus Euxinus). North of the city was a bay called the Golden Horn, with an invaluable harbor. A double line of protective fortifications went 6.5 km from the Sea of Marmara to the Golden Horn. This was completed during the reign of Theodosius II (408-450), under the care of his praetorian prefect Anthemius; the inner set was completed in CE 423. The Theodosian walls are shown as the limits of the "Old City" according to modern maps.


The Walls of Constantinople AD 324-1453, by Stephen R. Turnbull.

mla apa chicago
Your Citation
Gill, N.S. "Constantinople: Capital of the Eastern Roman Empire." ThoughtCo, Feb. 16, 2021, Gill, N.S. (2021, February 16). Constantinople: Capital of the Eastern Roman Empire. Retrieved from Gill, N.S. "Constantinople: Capital of the Eastern Roman Empire." ThoughtCo. (accessed March 23, 2023).