15. London, United Kingdom
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 crowned as the world’s largest financial centre and has the fifth- or sixth-largest metropolitan area GDP in the world. 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 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.