Greece, officially the Hellenic Republic, is a country in Southeast Europe. Located on the southern tip of the Balkan peninsula, it shares land borders with Albania to the northwest, North Macedonia and Bulgaria to the north, and Turkey to the east. The Aegean Sea lies to the east of the mainland, the Ionian Sea to the west, and the Sea of Crete and the Mediterranean Sea to the south. Greece has the longest coastline on the Mediterranean basin, spanning thousands of islands and nine traditional geographic regions. It has a population of over 10 million. Athens is the nation's capital and largest city, followed by Thessaloniki and Patras. Greece is considered the cradle of Western civilisation and the birthplace of democracy, Western philosophy, Western literature, historiography, political science, major scientific and mathematical principles, theatre, and the Olympic Games. The Ancient Greeks were organised into independent city-states, or poleis (singular polis), that spanned the Mediterranean and Black seas. Philip II of Macedon united most of present-day Greece in the fourth century BC, with his son Alexander the Great conquering much of the known ancient world from the Near East to northwestern India. The subsequent Hellenistic period saw the height of Greek culture and influence in antiquity.