Cahokia Woodhenge

The Cahokia Woodhenge was a series of large timber circles located roughly 850 metres (2,790 ft) to the west of Monks Mound at the Mississippian culture Cahokia archaeological site near Collinsville, Illinois, United States. They are thought to have been constructed between 900 and 1100 CE; with each one being larger and having more posts than its predecessor. The site was discovered as part of salvage archaeology in the early 1960s interstate highway construction boom, and one of the circles was reconstructed in the 1980s. The circle has been used to investigate archaeoastronomy at Cahokia. Annual equinox and solstice sunrise observation events are held at the site.