Tours and Excursions: The traditional way to see all of London's top attractions, these open-topped buses offer interesting commentary and plenty of opportunity to jump on and off when you reach an attraction that interests you. You can complete the tour in less than two hours and get a city overview, or you can spend all day at stops such as Speaker's Corner, Buckingham Palace, Westminster Abbey and St. Paul's Cathedral. Reliable and informative. Buses run every 10-20 minutes. TUBE: Green Park (for stop #1, though tickets can be purchased at each of the 30 stops)There are also lots of other bus tours in London, including Ensign, so shop around to see which one best suits you.