THE TOWER OF LONDON was first built by winiam the Conqueror， for the<br >purpose of protecting and controlling the city. As first planned， it lay<br >within the Roman city walls， but it.s enlargement in the thirteenth century<br >carried its boundaries eastwards beyond the walls. Nowadays it is wholly<br >within the borough of Tower Hamlets. Including the moat， it covers an<br >area of 18 acres (7.3ha).<br > Of the present buildings only the White Tower is of the Norman period;<br >but arehitoeture of almost all the styles which have flourished in England<br >may be found within the wails. The Tower has in the past been a fortress， a<br >palace and a prison， and has housed the Royal Mint， the Public Records and<br >(for a short time) tile Royal Observatory. It was for centuries the arsenal for<br >small arms and， being one of the strongest fortresses in the land， the Tower<br >has from early times guarded the Crown Jewels. From the thirteenth century<br >until 1834 it also housed the Royal Menagerie， the predecessor of the Lundon<br >Zoo.<br > The oldest and most important building is the Great Tower or Keep，<br >called the White Tower. The Inner Ward is defended by a wall containing<br >thirteen towers， the only surviving original entrance to it being that on the<br >south side under the Bloody Tower. The Outer Ward is defended by a<br >second wall， flamked by six towers on the river face， and by two semicircular<br >bastions at the north-west and north-east. A Ditch or Moat， now dry，<br >encircles the whole ; it is crossed at the south-western angle by a stone bridge，<br >formerly the drawbridge， leading to the Byward Tower from the Middle<br >Tower， where there was another drawbridge. In front of this was an outwork<br >