Built in 1080 on the site of a Roman camp which was enlarged into a Saxon
castles. The Norman keep added in 1130 is the tallest in England at over 100
foot high and has 12 foot thick walls. It was allowed to decay after the 15th
century until 1883 when it was opened to the public.
Parts of the 14/15th century city walls (which were first constructed in the 3rd century) still stand.