London is the capital city of England and the United Kingdom. With an estimated 8,308,369 residents as of 2012, London is the most populous region, urban zone and metropolitan area in the United Kingdom.Standing on the River Thames, London has been a major settlement for two millennial, its 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-mile medieval boundaries. With its population of 7,375 as of 2011, it is the smallest city in England. Since at least the 19th century, the term London has also referred to the metropolis developed around this core. London is a leading global city,with strengths in the arts, commerce, education, entertainment, fashion, finance, health care, media, professional services, research and development, tourism and transport all contributing to its prominence.It is one of the world's leading financiaL center's and has the fifth- or sixth-largest metropolitan area GDP in the world depending on measurement.London has been described as 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 in Europe.In 2012, London became the first city to host the modern Summer Olympic Games three times.