Yes, William the Conqueror was one of the most prolific castle builders in history, using them as a fundamental tool to subjugate and control the English population after the Norman Conquest in 1066. Before his arrival, England had very few fortified structures; William introduced the Motte-and-Bailey design, which could be constructed quickly using earth and timber. Over his 21-year reign, it is estimated that he and his nobles built nearly 500 castles across England to serve as military garrisons and administrative hubs. His most famous construction is the White Tower, the central keep of the Tower of London, which was built of stone to project an image of permanent, indestructible power. He also established the "Great Hall" at Windsor Castle and the formidable strongholds at Warwick, York, and Hastings. These castles were not just defensive structures; they were psychological symbols of the new Norman order. In 2026, many of the stone castles we see in England today stand on the original earthwork foundations laid by William’s engineers nearly a thousand years ago.