Oxford Castle is a large, partially ruined, medieval Norman castle in the city of Oxford, United Kingdom. The Abingdon Chronicle states that the castle at Oxford was built by the Norman knight Robert d'Oyly, an associate of William the the Conqueror. The castle was built in the western part of the city, on the banks of the River Isis (the name of the River Thames in Oxford). It's not known for certain whether there was Anglo-Saxon fortress on this site, but the existence of a town here is not questionable.
The original wooden castle belonged to the "motte-and-bailey" type and copied the castle built by Robert d'Oyly at Wallingford. In the middle of the twelfth century the castle was rebuilt in stone. This rebuilding primarily affected St George's Tower, the tallest and most powerful tower in the castle, which housed the chapel and crypt.
During the Baronial Wars, Robert d'Oyly Jr, nephew of Robert d'Oyly Sr, who had first been a supporter of King Stephen, then defected to the Empress Matilda. She took refuge in the castle during the siege for three months, then made a daring escape. Dressed in white so she couldn't be seen in the snow, Matilda, accompanied by only three or four of her knights, travelled down the castle wall, crossed the frozen River Isis and arrived safely at Abingdon. The next day the castle surrendered to King Stephen.
Over the following decades, the castle loses its military importance and gradually deteriorated. During the Civil War, the castle is still used Royalists as a fortress, but then it falls into complete disrepair and is used as a prison. Formally at this time the castle is owned by Christ Church College. In 1770, the castle was visited several times by John Howard, the famous humanist and philanthropist. His visits resulted in the reconstruction of Oxford Prison.
The prison was closed in 1996. The site is now a museum, shopping centre and business complex. Some of the prison cells have been converted into hotel rooms.
