The Palace of Westminster (Houses of Parliament) has three main towers. The largest is the 323ft tall Victoria Tower on the south-west corner of the Palace. Called 'King's Tower' at first, in honour of the then-reigning monarch William IV, the tower was a part of the palace's original design. The tower was re-designed several times, and its height increased each time. When completes in 1858, it was the tallest secular building in the world.
At the base of the tower is the Sovereign's Entrance, used by the monarch whenever entering the Palace to open Parliament. The main body of the Victoria Tower houses three million documents of the Parliamentary Archives in 5.5 miles of steel shelves spread over 12 floors. They include the master copies of all Acts of Parliament since 1497, and important manuscripts such as the death warrant of King Charles I. At the top of the roof is a 73 ft flagstaff which flies the Royal Standard when the Queen is present in the Palace. On the days when either House of Parliament is sitting the Union Flag flies from the mast.