London, England is actually two ancient cities that are now combined together. One of these two cities is the City of London, sometimes just called "the City," which is the business and financial center of the United Kingdom. The second ancient city is the City of Westminister, where Parliament and the majority of the government offices are located. The two cities combined are known as the region of Greater London.
London is the biggest city in Britain and Europe. It is located in the southeast area of England. The center of the city is marked by a plaque in the Church of St. Martin's in the Fields. Double-decker buses are a London icon. More than 300 languages are spoken in London. Four UNESCO World Heritage Sites are located in London: Maritime Greenwich, Westminister Palace, the Tower of London and Kew's Royal Botanic Gardens.
The first public zoo in the world opened in London in 1829. London is the only city to host the Olympics three times: 1908, 1948 and 2012. The London Underground, also known as "the Tube," became the first underground railway system ever constructed in 1863. London is also the greenest major city in the world, with 40 percent of its area devoted to parks and green space.