We attended one of the open houses held at Octagon. They close down the golf course and archeologists lead people out through the incredible earthworks, the largest geometric earthworks in the world! We were so impressed at the huge perfect circles at the site, and of course the acres big octagon. We never imagined something so important archeologically, here in Ohio. Try to visit on an Open House day when you can actually walk out across the area and explore inside of these amazing mounds, you can't help but be moved.