Located in Turkey, Constantinople became the new capital of the Roman empire in A.D. 324.

By A.D. 500, it was the largest city that remained after the fall of Rome. It too was shrinking under pressure from the Huns and other regional rivals.

In A.D. 537, the emperor Justinian I built the Hagia Sophia church.

Constantinople would decline to around 100,000 people by 700 before growing again, remaining one of the biggest cities in the west until the 18th century.