The United Kingdom of Great Britain and Northern Ireland is a sovereign state located off the northwestern coast of continental Europe. It is an island country, spanning an archipelago including Great Britain, the northeastern part of the island of Ireland, and many small islands. Northern Ireland is the only part of the UK with a land border, sharing it with the Republic of Ireland The United Kingdom is a constitutional monarchy and unitary state consisting of four countries: England, Northern Ireland, Scotland and Wales. It is governed by a parliamentary system with its seat of government in London, the capital. The UK has fourteen overseas territories that are not constitutionally part of the UK. These territories are remnants of the British Empire, which at its height in 1922 encompassed almost a quarter of the world's land surface, the largest empire in history. British influence can still be observed in the language, culture and legal systems of many of its former colonies. The UK is a developed country, with the world's sixth largest economy by nominal GDP and the sixth largest by purchasing power parity. It was the world's first industrialized country and the world's foremost power during the 19th and early 20th centuries. The UK nevertheless remains a major power with strong economic, cultural, military, scientific and political influence. It is a recognized nuclear weapons state and has the third or fourth highest defense spending in the world. It is a Member State of the European Union, a permanent member of the United Nations Security Council, a member of the Commonwealth of Nations, G8, G20, NATO, OECD and the World Trade Organization.