Portugal, officially the Portuguese Republic, located in southwestern Europe on the Iberian Peninsula, is the westernmost country of mainland Europe. Portugal is bordered by Spain to the north and east and by the Atlantic Ocean to the west and south. The Atlantic archipelagos of the Azores and Madeira are also part of Portugal. The territory which forms the modern Portuguese Republic has witnessed a constant flow of civilizations during the past 3,100 years, since the earlier pre-Roman inhabitants, to the Roman, Germanic, and Moorish peoples who made an imprint on the country's culture, history, language, and ethnic composition. During the 15th and 16th centuries, with its vast transcontinental empire, Portugal was one of the world's major economic, political, and cultural powers. A developed country, Portugal is a member of the European Union (since 1986), the United Nations (since 1955), and a founding member of the Eurozone, OECD, and NATO.