Built on the site of a Roman temple, the keep of Colchester Castle is the largest in Europe.
The castle is associated with Gundulf, Bishop of Rochester, William the Conqueror's great builder-priest. Work was started in about 1080. In 1085 the walls were fortified with battlements against a Danish attack. When the Danes didn't arrive work continued on the keep raising it to the height of three storeys or more. The keep with its inner and outer baileys, ditches and ramparts were probably complete by the beginning of the 12th century.
The castle remained the gift of the monarch to a succession of stewards. As the castle was too sombre to be a royal residence it later became a prison.
In 1683 the castle was bought by John Wheeley for the sake of its raw materials and he proceeded to dismantle the building. However, the castle was so well constructed that only the top could be removed.
In the mid 19th century the castle was acquired by Charles Gray who fostered local interest in the site.
The castle was gradually established as a museum and in 1931 the main building was roofed to provide galleries for the town's collection of Roman and British artifacts.