London is a leading global city, with strengths in the arts, commerce, education, entertainment, fashion, finance, research and development, tourism etc. It is one of the world's leading financial centres and has the fifth-or sixth-largest metropolitan area GDP in the world depending on measurement. London has five major business districts: the City, Westminster, Canary Wharf, Camden & Islington and Lambeth & Southwark. The West End is London's main entertainment and shopping district, attracting tourists. Europe's busiest shopping area is Oxford Street, a shopping street nearly 1 mile long, making it the longest shopping street in the United Kingdom. London is a major retail centre and it has the highest non-food retail sales of any city in the world.