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International status

The city acted as a defence for the eastern provinces of the old Roman Empire against the barbarian invasions of the 5th century. The 18-meter-tall walls built by Theodosius II were, in essence, impregnable to the barbarians coming from south of the Danube river, who found easier targets to the west rather than the richer provinces to the east in Asia. From the 5th century, the city was also protected by the Anastasian Wall, a 60-kilometer chain of walls across the Thracian peninsula. Many scholars argue that these sophisticated fortifications allowed the east to develop relatively unmolested while Ancient Rome and the west collapsed.

Constantinople's fame was such that it was described even in contemporary Chinese histories, the Old and New Book of Tang, which mentioned its massive walls and gates as well as a purported clepsydra mounted with a golden statue of a man. The Chinese histories even related how the city had been besieged in the 7th century by Mu'awiya I and how he exacted tribute in a peace settlement.