The period known as the Pax Romana, or "peace of Rome," began in the year 27 BC when Octavius took the throne as the Emperor Augustine, ending the period of civil wars and beginning the age of the emperors. In many respects this initiated a long period of incredible accomplishment, as the Empire expanded and was knit together by an amazing system of roads not equalled until the post-World War II era, and through the census, first introduced by Augustus. Roman cities boasted water systems, sewage systems, public transport and many other "modern" advantages. The Pax encompassed the era of "the Five Good Emperors." Unfortunately, at the same time the ideals of the Roman Republic died a hard death, with increasing tyranny by the emperors, corruption in the government, and a general decline in the ability and desire of the citizens to take responsibility for their society.
Law and order was an essential ideal of the Pax, and an increasing prosperity accompanied the advances of the Empire. In general, in the 200 years of the Peace, things went well for the Empire as a whole and for Roman citizens generally. The Senate still functioned fairly well, and it was not until late in this period that things began to slip badly. The Great Fire occurred in AD 64, but Rome was rebuilt as a city of epic architecture. The Colosseum was completed in 80, the Pantheon in 130 and the Empire reached its greatest extent by 138. But the Peace of Rome was actually a period of war and conquest on the borers of the Empire, and the very success of the Roman military led to unrest on those borders. By 235 the Period of Anarchy had begun, and the long decline of Rome was underway. Today the Pax Romana is generally defined as having ended by the year 180.
Art, architecture and culture was greatly influenced by Greek culture, but the laws were originally firmly based in the Roman Republican tradition. That unfortunately changed as corruption increased, and the public was generally used by the ruling elite as a source of political power through manipulation rather than appeals to good citizenship. After the Pax the decline of Rome accelerated, and although much has been made of the decline of public morals the real cause of Rome's collapse was the decline of the interest of the citizens in service in the Roman military. By the period of anarchy the Roman armies were dependant on mercenaries, largely from the Germanic lands. Their acquaintance with Roman military methods and the state of the empire generally led eventually to the attacks of Germanic peoples on the Roman lands, and the eventual collapse of the Western Empire.