one of the oldest and most famous buildings in London, England. It is an ancient fortress (= strong castle) on the north bank of the River Thames to the east of the city, and is a popular tourist attraction. It was made a World Heritage Site in 1988.The building of the Tower was begun in the 11th century by William the Conqueror, and completed in the 13th century. At various times it was a royal palace, the last monarch to live there being James I in the early 17th century. It is best known, however, as a prison in which many famous people accused of crimes against the king or queen were kept. These included Anne Boleyn and Thomas More.The Tower of London has many well-known features. These include the White Tower, which is the oldest part, the Bloody Tower, where some prisoners were kept, and Traitor's Gate, an entrance for prisoners on the bank of the river. The Crown Jewels have been kept there since 1303 and are on public display. Perhaps the most famous image associated with the Tower is that of the Yeoman Warders, the official guards, who are also known as beefeaters. They were established in the 16th century and still wear costume of the Tudor period.