Abingdon Castle is a historic site located in Abingdon-on-Thames, England. Originally built in the 11th century, it served as a royal residence and a defensive structure. The castle was constructed during the reign of William the Conqueror and played a significant role in the region's history. Today, only remnants of the castle remain, including sections of the walls and a few foundations. The site is a popular attraction for visitors interested in medieval history and architecture. Nearby, the Abingdon Abbey and the River Thames add to the area's historical significance and charm.