Parts of the earthworks of some such fortifications still exist. The earthen mounds are the most visible earthworks at the site. Evidence of Neolithic activity includes monumental earthworks or barrows such as that at Margery Hill. The county is rich in archaeological remains such as forts, earthworks and standing stones. They also constructed large cult centres surrounded by pales, earthworks and moats. Military earthworks can result in subsequent archaeological earthworks. They are used to protect harbour walls, breakwaters and shore earthworks. Large long barrows like White Barrow and other earthworks were built across the plain. The monument consists of a stone circle surrounded by massive earthworks and a ditch. Interest in the prehistoric culture that built the Marietta Earthworks continued. The structures were usually open-topped concrete walls protected by sloped earthworks. By 1975, earthworks and a storm drainage system had been completed. Encountering the Confederate earthworks manned by Brig. The state built a museum devoted to interpreting the earthworks and the artifacts uncovered there. It was fortified by surrounding it with earthworks.