The Waterloo Barracks: best known as the current home of the Crown Jewels. Photography inside the building is prohibited (visit Her Majesty's website for images of the jewels) but here is a shot of the outside.
The Crown Jewels have been in the Tower since the 1300s. The only exception was WWII, when they were removed to a secret location, returning to the Tower in 1945 at the end of the war.
The Tower of London