aerial photograph of Colchester Castle , England. The Castle is Europes largest surviving Norman keep and was built on the site of the Roman temple burned down by Boudica in the revolt against Roman rule. The castle was attacked and captured by King John in the first barons Rebellion of 1215. In 1645 suspected Witches were imprisoned and tortured here by the Witchfinder General. The castle was partially demolished in the 17th century but by the 18th century the first attempts at conservation were made. The castle is now preserved as a museum and open to the public.