The keep, dating from about 1173, is among the oldest in Northumberland, while the rest of the castle was built mainly in the 13th century. It was in a semi-ruinous state by the late 16th century but was partially restored by the 2nd Duke of Northumberland between 1808 ans 1818. The castle is situated on the north side of the Prudhoe and is open all year, English Heritage standard opening times. It contains a fascinating exhibition of castles in Northumbria.