London, UK- the capital of England and the United Kingdom, is a 21st-century city with history stretching back to Roman times. At its center stand the imposing Houses of Parliament, the iconic ‘Big Ben’ clock tower, and Westminster Abbey, site of British monarch coronations. Across the Thames River, the London Eye observation wheel provides panoramic views of the South Bank cultural complex and the entire city. London had the second-highest number of ultra-high-net-worth individuals in Europe, after Paris and in 2020; London had the second-highest number of billionaires of any city in Europe, after Moscow. London's universities form the largest concentration of higher education institutes in Europe, and London is home to highly ranked institutions such as Imperial College London in natural and applied sciences, the London School of Economics in social sciences, and the comprehensive University College London. London contains four World Heritage Sites: the Tower of London; Kew Gardens; the site comprising the Palace of Westminster, Westminster Abbey, and St Margaret's Church; and the historic settlement in Greenwich where the Royal Observatory, Greenwich defines the Prime Meridian (0° longitude) and Greenwich Mean Time. Other landmarks include Buckingham Palace, the London Eye, Piccadilly Circus, St Paul's Cathedral, Tower Bridge, Trafalgar Square, and The Shard, etc...