The United Kingdom of Great Britain and Northern IrelandThe United Kingdom of Great Britain and Northern Ireland (commonly known as the United Kingdom, the UK or Britain) is a sovereign state off the north-western coast of continental Europe. The country includes the island of Great Britain, the north-eastern part of the island of Ireland and many smaller islands. Northern Ireland is the only part of the UK that shares a land border with another sovereign statethe Republic of Ireland. Apart from this land border the UK is surrounded by the Atlantic Ocean, the North Sea, the English Channel and the Irish Sea.The UK is a developed country and has the worlds sixth-largest economy by nominal GDP and seventh-largest economy by purchasing power parity. It was the worlds first industrialized country and the worlds foremost power during the 19th and early 20th centuries although the economic and social cost of two world wars and the decline of its empire in the latter half of the 20th century diminished its leading role in global affairs. The UK nevertheless remains a great power with leading economic, cultural, military, scientific and political influence. It is a member state of the European Union, a permanent member of the United Nations Security Council, and is also a member of: the Commonwealth of Nations, G8, G20, NATO, the OECD, the Council of Europe and the World Trade Organization.London contains four World Heritage Sites: the Tower of London; Kew Gardens; the site comprising the Palace of Westminster, Westminster Abbey and St Margarets Church; and the historic settlement of Greenwich (in which the Royal Observatory marks the Prime Meridian (0 longitude) and GMT). Other famous landmarks include Buckingham Palace, the London Eye, Piccadilly Circus, 30 St Mary Axe (The Gherkin), St Pauls Cathedral, Tower Bridge and Trafalgar Square. London is home to numerous museums, galleries, libraries, sporting events and other cultural institutions including the British Museum, National Gallery, British Library, Wimbledon and 40 theatres.The Tower of LondonKew GardensThe Palace of WestminsterBig Ben