文档介绍：For over 900 years, the Tower of London has served as a loyal __1__
palace and fortress. Today, it's famous for its bloody history and
for being the place where the Crown Jewels are it has served
for other purposes, too. It has been the royal arsenal, royal mint, __2__
royal observatory or even the royal zoo. The site of the Tower was __3__
originally part of the Roman city of Londinium.
But, in 1066, a foreigner from north west France became King William __4__
of Britain, he ordered that a wooden castle built on the banks of __5__
the river Thames. The purpose of this fortress was to help secure
London, the most important city in his view realm. Ten years later,
William had the fortress rebuild in stone, and created a great __6__
fortified palace with walls three metre thick. Today, this building __7__
is known as the White Tower, and it stands in the centre of a much 
larger stone fortress, which was built during later centuries. The
Tower now covers the area of seven hectares, and it stands near the __8__
busy financial district of the capital. But, once inside the high stone
walls, it's easy to forget the modern world outside and to take a
trip back through history. To help visitors explore, there are special
ceremonial guards, called Yeoman Warders. They are also known as 
Beefeaters, and they are the best resource of information about the __9__