On the bluff a quarter of a mile north, ancient Indians predating the Aricara built a fortress or strong point with an exterior perimeter of over 2,000 yards enclosing about 50 acres. Bastions stood at intervals along its palisaded wall to provide enfilading arrow fire, and a deep dry moat lay in front. Within the palisades were many square or oblong Indian houses, and a valley in the center contained an abundance of water. Five thousand people could have been sheltered within its walls, and it would have taken not less than 300 resolute warriors to defend it. Archaeologists date it to the time of Columbus or earlier, and the probability of influence from white military design appears remote. Though bastions and enfilading fire are identified as white inventions, this fortress is presented as evidence that Native people also possessed military genius, and its bastions, watch guard fire points, and moats are still visible.