Once the tiltyard for jousting tournaments, Horse Guards Parade is best known for the annual Trooping the Colour ceremony, in which the Queen takes the salute on her official birthday tribute, on the second Saturday in June. (Though it's called a birthday it's actually the anniversary of her coronation—the Queen's real birthday is on April 21.) It's a must-see if you're around, with marching bands and throngs of onlookers. Throughout the rest of the year the changing of two mounted sentries known as the Queen's Life Guard at the Whitehall facade of Horse Guards provides what may be London's most popular photo opportunity. The ceremony last about half an hour.
London, SW1A 2AX, England