Ancient Greece was a northeastern Mediterranean civilization, existing from the Greek Dark Ages of the 12th–9th centuries BC to the end of classical antiquity, that comprised a loose collection of culturally and linguistically related city-states and other territories. Prior to the Roman period, most of these regions were officially unified once under the Kingdom of Macedon from 338 to 323 BC. In Western history, the era of classical antiquity was immediately followed by the Early Middle Ages and the Byzantine period.