Augustus, the first Roman emperor, ruled for 45 years.  It was during the reign of Augustus that people got used to being ruled by one leader.  Rome went on to greatness under the Empire, but the Roman Republic was no more. For 45 years, Rome was at peace. This period is the beginning of the Pax Romana, or Roman Peace. The phrase "Roman Peace" is a bit misleading. The Romans continued to expand their empire during this period. They did not always do so peacefully. Things were not always peaceful in the city of Rome. Rome did not always have the best leadership. Some emperors were very cruel. Some were insane. But the empire continued to be stable. For around 200 years, the Roman Empire was united.  The Romans were great builders. Many of their incredible buildings and engineering projects were constructed during this period of relative peace. Culture and literature flourished. Much of Greek culture was adopted during this period.   Pax Romana