London is the capital city of England and the United Kingdom and its history extends over 2000 years. London is incredibly well connected, with five international airports and the high-speed Eurostar rail link. More than 50 countries are within a three-hour flight time and upwards of 300 international destinations have direct links to the city. The capital has become one of the world’s most significant financial and cultural capital cities. The City of London often referred to simply as “the City”, is the historic core of the Greater London area and is today its primary financial district, although it represents only a small part of the wider metropolis. London's world-class tourist attractions are renowned across the globe and the city boasts four World Heritage Sites: the Palace of Westminster and Westminster Abbey, the Tower of London, Maritime Greenwich, and the Royal Botanic Gardens, Kew. Many of the most famous attractions are free to visit, for example, Tate Modern, the National Gallery, and the Victoria and Albert Museum. The River Thames runs through the heart of London, from Richmond in the west, through the central London borough of Westminster, to Greenwich in the east. London river cruises and river buses are a great way to see the city.