William the Conqueror built the vast, gloomy Tower of London after his 1066 invasion, mostly to cow the natives. He was also known as William the Bastard, but not to his face. In spite of the crowds, the Tower retains an aura of dread. This is where two of Henry VIII's wives arrived through Traitor's Gate, at left, to be executed. Oh yeah, and don't miss the Crown Jewels.