The basis of the Tower of London is the innermost White Tower, built by William the Conqueror in 1078. Subsequent rulers expanded it over the centuries to include additional walls, wards and moats.
Though it often served as a fortress to defend the crown, the Tower's most infamous use was as a prison--and occasional execution site--for royal captives. Notable prisoners in the Tower include Anne Boleyn, Henry VI, Sir Walter Raleigh and Elizabeth I who was imprisoned there for a short time before she became queen.
Since 1303, the Tower has held the Crown Jewels of the United Kingdom. They are available for public display, but closely guarded. The king or queen wears them only during the coronation or for certain state functions.
The 35 Yeoman Warders, also known as "Beefeaters," are stationed in the Tower at all times in order to protect it. Though they mainly serve as tour guides these days, they are all trained members of the British military with at least 22 years of experience apiece.
According to tradition, there must be at least six ravens in residence at the Tower at all times. If there aren't, the Tower, the monarchy and the kingdom will fall.
