Ancient Rome

Diocletion attempted to stabilize the Roman Empire by splitting it into two (and later four) regions with four rulers -- also known as the Tetrarchy, with each ruler picking a successor (Mathisen). Since the time of Caesar, it had essentially become too big to be governed by one ruler. Thus, Diocletian's re-ordering of the empire was a way to make governance more practical and possible (Khan Academy). He himself took over governance of the Eastern half with its base in Constantinople while appointing a co-ruler for the Western half. Later to keep out the Visigoths, Diocletian also appointed two more rulers to help keep the barbarians from invading. In doing so, Diocletian began the practice of subdividing provinces into dioceses -- and creating a hierarchy of governance from the local level on up to the imperial level. This is where the Catholic Church adopted its diocesan rule from. By subdividing provinces, Diocletian was able to exercise more control over the barbarian armies

Diocletian also undertook other reforms to help bring stability to the empire. This included economic reform, such as the payment in kind system that Diocletian adopted to help offset the debasement of the currency and the rise of inflation. He also undertook... To unify the empire along religious grounds, he attempted to force Christians to embrace the Roman cult.
Constantine also made some reforms to try to stabilize the empire. He reversed the policy of Diocletian regarding the Christians with the Edict of Milan, which allowed Christians to worship publicly. He also reversed Diocletian's policy on multiple leaders, doing away with the other Roman rulers). He also moved the capital of Rome to Constantinople and addressed the issue of the currency, which Diocletian had been unable to solve (Constantine introduced the solidus, a new currency that the people accepted in confidence). Constantine also set about tying labor to the land and introducing agrarian reform as well wage and price fixing to combat inflation ("Diocletian and Constantine").

The environment was not in good condition in Rome. People were leaving the city and the Germanic tribes were destabilizing the realm. Constantine had abandoned Rome for Byzantium, which he renamed after himself to Constantinople (Khan Academy). The architecture under Constantine was consistent, however, with what had come before. The triumphal arch was still an architectural staple,…