Monks Mound is the largest Pre-Columbian earthwork in America north of Mesoamerica. Located at the Cahokia Mounds UNESCO World Heritage Site near Collinsville, Illinois, its size was calculated in 1988 as about 30 m high, 291 m long including the access ramp at the southern end, and 236 m wide. This makes Monks Mound roughly the same size at its base as the Great Pyramid of Giza. Its base circumference is larger than the Pyramid of the Sun at Teotihuacan.