Welcome to England's capital and largest city, London, located in the U.K. A 50-mile-long estuary of the Thames flows 80 kilometers (50 miles) into the North Sea from London. Originally called Londinium, London has been a significant settlement for two millennia. The Romans established it. "The Square Mile" is a colloquial term for the City of London, London's ancient core and financial center, which covers just 1.12 square miles (2.9 km2) and retains medieval boundaries. Westminster, a nearby city, has been home to much of the nation's government for centuries. Modern London also includes 31 additional boroughs to the north and south of the Thames River. The Mayor of London is responsible for governing London and also the London Assembly. London is a major global city. There are many areas in which it has a significant impact on society: the arts, commerce, and education; entertainment and fashion; finance; healthcare; media; professional services; research and development; tourism and transportation. A central financial hub, London was Europe's second-highest concentration of ultra-high net worth individuals in 2019. Aside from Moscow, London is expected to have the second-highest number of billionaires in Europe by 2020. Imperial College London, a university specializing in the natural and applied sciences, the London School of Economics, a school specializing in social sciences, and the University College London, a comprehensive research university, are among the most prominent higher education institutions in Europe. For the first time in modern summer Olympic history, London hosted three stylish summer Olympic games in 2012. Almost 300 languages are spoken in the Greater London area. With an estimated population of 9 million as of mid-2018, it is the third-most populous city in Europe.13,4 percent of the U.K.'s population lives in the town of London as of 2011, the Greater London Built-up Area had 9,787,426 residents, making it Europe's fourth-most populous metropolitan area after Istanbul, Moscow, and Paris. With 14,040,163 residents in 2016, the London metro area is the third most populous in Europe, behind Istanbul and the Moscow Metropolitan Area. There are world heritage sites in London: The Tower of London, Kew Gardens, Westminster Abbey, and St Margaret's Church, as well Greenwich, where the Royal Observatory, Greenwich, defines the Prime Meridian (0 longitude) and Greenwich Mean Time. As well as Buckingham Palace and the London Eye, othe