The Castle On The Hill Historical Marker, found at 809 Oak Ridge Turnpike, is a vital piece of Oak Ridges history. Built in 1943, it served as a chapel for workers at the nearby atomic research facility - making it one of the citys most notable landmarks. Nestled within the Secret City Commemorative Walk, which includes other significant sites like the Chapel on the Hill and the Alexander Guest House, the Castle On The Hill Historical Marker offers insight into Oak Ridges beginnings during World War II when it was a Secret City that played a crucial role in developing nuclear technology.