London is the capital and most populous city of England and the United Kingdom. Standing on the River Thames in the southeast of the island of Great Britain, London has been a major settlement for two millennia. Londinium was founded by the Romans. The City of London, London's ancient core − covering an area of just 1.12 square miles (2.9 km2) and nicknamed the Square Mile − retains its medieval boundaries. The City of Westminster is an Inner London borough which also holds city status. It occupies much of the central area of Greater London including most of the West End. It is to the west of the City of London. Greater London is governed by the Mayor of London and the London Assembly.
London is a leading global city in the arts, commerce, education, entertainment, fashion, finance, healthcare, media, professional services, research and development, tourism and transportation. London, the fourth fastest-growing city, is 26 out of 300 major cities for economic performance. It is one of the largest financial centres and has either the fifth or sixth largest metropolitan area GDP. It is the most-visited city as measured by international arrivals and has the largest city airport system measured by passenger traffic. It is the leading investment destination, hosting more international retailers and ultra high-net-worth individuals than any other city. London's universities form the largest concentration of higher education institutes in Europe. In 2012, London became the first city to have hosted three modern Summer Olympic Games.
London has a diverse range of people and cultures, and more than 300 languages are spoken in the region. Its estimated mid-2016 municipal population (corresponding to Greater London) was 8,787,892, the largest of any city in the European Union and accounting for 13.4% of the UK population. London's urban area is the second most populous in the EU, after Paris, with 9,787,426 inhabitants at the 2011 census. The city's metropolitan area is the most populous in the EU with 14,040,163 inhabitants in 2016, while the Greater London Authority states the population of the city-region as 22.7 million. London was the world's most populous city from c.1831 to 1925.
London contains four World Heritage Sites: the Tower of London; Kew Gardens; the site comprising the Palace of Westminster, Westminster Abbey, and St Margaret's Church; and the historic settlement of Greenwich (in which the Royal Observatory, Greenwich defines the Prime Meridian, 0° longitude, and GMT). Other landmarks include Buckingham Palace, the London Eye, Piccadilly Circus, St Paul's Cathedral, Tower Bridge, Trafalgar Square and The Shard. London is home to numerous museums, galleries, libraries, sporting events and other cultural institutions, including the British Museum, National Gallery, Natural History Museum, Tate Modern, British Library and West End theatres. The London Underground is the oldest underground railway network in the world.