One of the Junction Group's large sacred circles stands among Ohio's many geometric earthworks, the large majority of which are circles. Many of Ohio's more than 600 geometric earthworks were built by the earlier pre-Hopewell Adena culture as long as 2,500 years ago. Some were as small as 50 feet across, while others grew much larger, including Newark Ohio's Great Circle at more than 1,200 feet across. The circular earthworks at Junction are relatively small and were probably among the earliest Hopewell enclosures to be built. Their precision was rediscovered through a detailed magnetometry image produced by teams led by Dr. Jarrod Burks of the Heartland Earthworks Conservancy. Many Hopewell earthworks consist of near-perfect circles, squares, and other shapes, and a few include long avenues flanked by parallel embankment walls. Some circles and squares have equal areas, multiple sites across the region used standard units of measure, and earthwork geometry was often aligned with key sun and moon-rises. Together, these features show that the American Indian builders of these ancient monuments had sophisticated systems of shared knowledge.