London is the capital city of England and the United Kingdom and a leading global city, with strengths in the arts, commerce, education, entertainment, fashion, finance, healthcare, media, professional services, research and development, tourism and transport all contributing to its prominence. 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. In 2012, London became the first city to host the modern Summer Olympic Games three times. London had an official population of 8,308,369 in 2012, making it the most populous municipality in the European Union, and accounting for 12.5% of the UK population.