Most of the immediate successors of Augustus Caesar except for Marcus Aurelius were weak, incompetent and tyrants. Caligula and Nero were the worst examples for a bad Ruler. Roman Civilization was on a decline and Diocletian and his successors checked it to some extent.

Emperor Constantine shifted the capital of the Roman Empire from Rome to Constantinople, a city named after him in 330 CE which marked the beginning of the Eastern Roman Empire. Constantinople was built on the ancient site of Byzantium which is now called Istanbul, located in Turkey. He issued the edict of Milan, which granted liberty to Christians to profess their religion and began the Christianization of the Empire.

Justinian was the last great Emperor who had control over both the Eastern and the Western halves of the Empire. His long-lasting achievements were the ‘Justinian code’ and his buildings in Constantinople. The Eastern Roman Empire with Constantinople as its capital continued to exist till it was overthrown by the Turks in 1453 CE.