Buckingham Palace has been the Queen's official residence since 1837 (when Queen Victoria decided St James's Palace, just down the road, was too small and unimpressive). Read more.
The 86th-floor observatory is 1,050 feet (320 m) high, and if you pay a little extra you can visit the more intimate, enclosed observatory on the 102nd floor at 1,224 feet (373 m). Read more.
The London Eye is the fourth-tallest structure in London, so the far-reaching views over London are spectacular. On a clear day you can see as far as Windsor Castle. Read more.
It's the only spot in the United States from which humans have been hurled into space! Read more.