London is a place.
London . It was founded by the Romans , who named it Londinium . London 's ancient core , the City of London , largely retains its 1.12 sqmi medieval boundaries . London is a leading global city in the arts , commerce , education , entertainment , fashion , finance , healthcare , media , professional services , research and development , tourism , and transportation . London was the world 's most populous city from around 1831 to 1925 .