Ancient Greece was an ancient civilization existing from the Greek Dark Ages of the 12th–9th centuries BC to the end of classical antiquity, comprising a loose collection of culturally and linguistically related city-states and regions, primarily centered in the northeastern area of the Mediterranean Sea. Prior to the Roman period, most of this area was officially unified only once, from 338 to 323 BC under the Kingdom of Macedon. In Western history, the era of classical antiquity was immediately followed by the Early Middle Ages and the Byzantine period.