Ancient Rome was a civilization that grew from a small agricultural community founded on the Italian Peninsula circa the 9th century BC to a massive empire straddling the Mediterranean Sea. In its 12-century existence, Roman civilization shifted from a monarchy, to a republic based on a combination of oligarchy and democracy, to an autocratic empire. It came to dominate Western Europe and the entire area surrounding the Mediterranean Sea through conquest and assimilation.
The Roman empire went into decline in the 5th century AD. The western part of the empire, including Hispania, Gaul, and Italy, broke into independent kingdoms in the 5th century. The eastern empire, governed from Constantinople, is usually referred to as the Byzantine Empire after 476. This is the traditional date for the "fall of Rome" and for the onset of the Early Middle Ages, also known as the Dark Ages.
Roman civilization is often grouped into "classical antiquity" with ancient Greece, a civilization that inspired much of the culture of ancient Rome. Ancient Rome contributed greatly to the development of law, war, art, literature, architecture, technology and language in the Western world, and its history continues to have a major influence on the world today.