Oxford Castle is a large, partly ruined Norman medieval castle situated on the west edge of Oxford . The original moated, wooden motte and bailey castle was replaced with stone in the 11th century and played an important role in the conflict of the Anarchy. In the 14th century the military value of the castle diminished and the site became used primarily for county administration and for detaining prisoners. Most of the castle was destroyed during the English Civil War and by the 18th century the remaining buildings were used as Oxford's local prison.
A new prison complex was built on the site from 1785 onwards and expanded in 1876; this ultimately became HM Prison Oxford. The prison closed in 1996 and was redeveloped as a hotel. Today the medieval remains of the castle, including the motte and St George's Tower, are classed as a Grade I listed building and as a Scheduled Monument.