Castle Acre Castle is a historic site located in Norfolk, England. Built in the late 11th century, it was established by William de Warenne, a companion of William the Conqueror. The castle features a motte-and-bailey design, with a large earthwork mound and a surrounding defensive ditch. The castle played a significant role in the medieval period, serving as a royal fortress and administrative center. Today, it is a scheduled ancient monument, attracting visitors who come to explore its ruins and learn about its rich history. The site is managed by English Heritage.