The Hopewell constructed earthworks in combinations of circles, squares, and octagons, sometimes incorporating other shapes such as the D-shaped enclosure at Hopewell Mound Group. At five sites within a few miles of each other along the main channel of Paint Creek—Seip, Baum, Works East, Liberty, and Frankfort—the designs are strikingly similar, with each including a large circle, a small circle, and a square of nearly equal size. The common purpose of these forms and the significance of their size and shape remain unknown, though one possibility is that they were designed as primitive observatories with unique alignments tracking astronomical events such as the movement of the sun and moon. The east wall at Hopewell Mound Group, pictured in 1891, was once six feet high, while the walls of the square enclosure were lower and now are invisible. Similar building designs also appear at Seip Earthworks, Seal Works, Hopewell Mound Group, and many other sites, each with a large enclosure and an attached square whose purpose is unknown.