London is the capital city of both England and the United Kingdom, located on the River Thames in southeast England. It has a population of over 8 million and is visited by nearly 30 million people annually. Some of London's most famous landmarks include the Tower of London, Tower Bridge, St. Paul's Cathedral, Buckingham Palace, Big Ben, Hyde Park, Piccadilly Circus, and Trafalgar Square. London has over 240 museums and is known for its double decker buses, black taxis, and extensive underground metro system.