York had two motte and bailey castles, one on either side of the River Ouse, which date from the time of the Norman conquest of the north.
What is now known as York Castle is situated north-east of the Ouse. The surviving motte is 14.60 m (48 feet) high and up to 71.6 m (235 feet) wide (although it has been enlarged since Norman times). It was part of the first castle built in York by William the Conqueror in 1068 which was attacked by a force of Danes and local people in 1069. Originally there was a ditch around the base of the motte and a bailey to the north-west and south-east. The latter is now defined by later medieval walls. To the south-east the River Foss was dammed to make the King's Fishpool providing the castle with extra defence and a food supply. The original keep was a timber structure which was burnt down in 1190 by rioters attacking the local Jewish community who were sheltering inside. The present stone keep is mid 13th century in origin.
A second castle, south-west of the Ouse, known today as Baile Hill, is thought to have been built after the attack on York in 1069. The motte today is a tree-covered mound c. 12.20m (40 feet) high and stands in the south-east corner of the medieval walled city. Excavations showed that it was built of horizontally laid layers of earth and revealed steps leading to a timber structure on the top. The bailey defences survive as ramparts on its south-east and south-west sides which are now incorporated into the defences of the city itself.
Addyman, P.V. and Priestley, J., 1977. 'Baile Hill, York: a report on the Institute's excavations', Archaeological Journal 134, 115-56
Royal Commission on Historical Monuments (England), 1972. An Inventory of the Historical Monuments in the City of York, 2: The Defences (London, HMSO)