London is the capital and most populous city of England and the United Kingdom. Standing on the River Thames in the south east of the island of Great Britain. London is a leading global city in the arts, commerce, education, entertainment, fashion, finance, healthcare, media, professional services, research and development, tourism and transportation. It is the world's largest financial Centre and has the fifth or sixth largest metropolitan area GDP in the world. London is often regarded 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. It is the world's 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 the modern Summer Olympic Games three times.