Monks Mound is the largest prehistoric earthen structure in North America and the centerpiece of the Cahokia Mounds site. At 100 feet tall and covering more ground at its base than the Great Pyramid of Giza, it was built entirely by hand over several centuries, with workers carrying basket-loads of soil up an ever-growing platform. The mound has four terraces and once supported a large wooden building — presumably the residence of the paramount chief — on its summit.
The climb takes about ten minutes on the maintained path and the view from the top is genuinely arresting: the flat American Bottom stretching west toward the Gateway Arch visible on the St. Louis skyline, and the surviving mounds dotting the landscape below. It puts the ancient city into immediate physical perspective in a way the museum cannot.