Cambridge Castle is an earthwork motte and bailey fortress, founded in 1068 by King William I. In the late 13th century, King Edward I founded the stone castle, when adding a curtain wall flanked by towers, a large twin-towered gatehouse and a keep on the motte. Dilapidated by 1441, it was described as 'old, ruined and decayed' in 1590 but the castle was refortified during the civil war. Brick barracks were built on the site of the great hall but in 1647 the new defences were slighted. The gatehouse and barracks were retained as prison buildings, until the early 19th century and the Shire Hall of 1932 now stands in the levelled bailey. An outer bailey may have existed to the north but only the motte and damaged civil war earthworks of bastions and ramparts now remain.