Norwich Castle.

“Norwich Castle was founded by William the Conqueror some time between 1066 and 1075. It originally took the form of a motte and bailey. Early in 1067, William the Conqueror embarked on a campaign to subjugate East Anglia, and according to military historian R. Allen Brown it was probably around this time that Norwich Castle was founded. The castle is first mentioned in 1075 when Ralph de Gael, Earl of Norfolk, rebelled against William the Conqueror and Norwich was held by his men. A siege was undertaken, but ended when the garrison secured promises that they would not be harmed.”