Where was the Byzantine Empire?

The Byzantine Empire's geography shifted dramatically over its millennium-long history, but its heart was always Constantinople — modern Istanbul, Turkey. Founded by Constantine I in 330 CE on the site of the ancient Greek city of Byzantium, Constantinople occupied one of the most strategically valuable locations in the world: the narrow Bosporus strait connecting the Mediterranean and Black Seas, and the land bridge between Europe and Asia.

At its greatest territorial extent under Justinian I (mid-6th century), the Byzantine Empire encompassed an enormous area: all of modern Turkey, Greece, and the Balkans; the entire eastern Mediterranean coast (modern Syria, Lebanon, Israel, and Jordan); Egypt and Libya across North Africa; Tunisia; all of Italy; and parts of southern Spain. This represented a genuine attempt to restore the boundaries of the old Roman Empire.

However, the Arab conquests of the 7th century permanently stripped away the empire's wealthiest provinces: Egypt, Syria, and North Africa. From the 7th century onward, the empire was primarily an Anatolian and Balkan state, centered on modern Turkey and Greece. Even this reduced territory was further eroded by Seljuk Turkish expansion after the Battle of Manzikert (1071), which opened Anatolia to Turkish settlement.

By its final centuries, the Byzantine Empire had shrunk to little more than Constantinople itself and a few surrounding territories. When the city finally fell to the Ottoman Turks in 1453, the empire that had once stretched from Spain to Mesopotamia had been reduced to a single, magnificent, dying city. Yet Constantinople's strategic location ensured its continued importance — the Ottomans made it their capital, and Istanbul remains Turkey's largest and most important city today.