London is the capital and most populous city of England and the United Kingdom. Standing on the River Thames, London has been a major settlement for two millennia, it history going back to its founding by the Romans, who named it Londinium. London's ancient core, the City of London, largely retains its 1.12 square miles (2.9 km) medieval boundaries. Since at least the 19th century, the term London has also referred to the metropolis developed around this core. The bulk of the conurbation forms the Great London administrative area governed by the Mayor of London and the London Assembly.
London is the leading global city, with strengths in the arts, commerce, education, entertainment, fashion, finance, healthcare, media, professionals services, research and development, tourism and transport all contributing to its prominence. It is one of the world's leading financial centers and has the fifth largest metropolitan area GBP in the world depending on measurement. London is a world cultural capital. It is the world's most visited city as measured by International arrivals and has the world's largest city airport system measured by passenger traffic. London's 43 universities form the largest concentration of higher education institutes in Europe.
London contains four World Heritage Sites; the Tower of London, Kew Gardens, the sit comprising the Palace of Westminster, Westminster Abbey and St. Margaret's Church; and the historic settlement of Greenwich (in which the Royal Observatory, Greenwich marks the Prime Meridian, 0" longitude and GMT). Other famous landmarks include Buckingham Palace, the London Eye, Piccadilly Circus, St. Paul's Cathedral, Tower Bridge, Trafalgar Square and the Shard. London is the home to numerous museums, galleries, libraries, sporting events and other cultural institutions, including the British Museum, National Gallery, Tate Modern British Library and 40 West End theaters. The London Underground is the oldest underground railway network in the world.