Roman civilization originated in the city of Rome, founded in the 8th century BC along the Tiber River. According to legend, Rome was founded by Romulus and Remus. Roman society was divided between patricians and plebeians, and later included slaves. The government transitioned from a monarchy to a republic to an empire. The Roman Empire reached its peak between the 1st and 2nd centuries AD during the Pax Romana, but economic and political crises led to the Western Empire's fall in 476 AD. Roman influence is still seen today through language, laws, and Christianity.