Wolvesey Castle, also known as the "Old Bishop's Palace", is a ruined building in Winchester, Hampshire, England that was a bishop's palace, and was briefly fortified during the later years of Henry of Blois, the Bishop of Winchester. The first building on the site, an eyot in the River Itchen known as "Wulveseye" or Wulf's island, was constructed around 970 by Æthelwold of Winchester, the Bishop of Winchester from 963 to 984, as his official residence or palace. Winchester came under siege during the Rout of Winchester in 1141 by the Empress Matilda during the period of civil war known as The Anarchy, and held out for three weeks until relieved by Stephen's wife, Matilda. Subsequently Henry, the brother of Stephen, King of England, enlarged and fortified the palace by building a curtain wall, giving the palace the appearance of a castle. The fortifications were slighted by Henry II after the death of Henry in 1171.