Do not be fooled by these humble hills—the Cahokia Mounds State Historic Site is actually the archeological remains of the largest and most sophisticated prehistoric civilization North of Mexico! The ancient settlement covers 2,200 acres of land and has revealed artifacts dating back to 700 AD! There are over 100 human-made mounds of all shapes and sizes spread across the site that served a variety of purposes in the native culture, the largest of which—the Monks Mound—is a platform-style pyramid over 100 feet tall and has a base as broad as the Giza Pyramid in Egypt! Some of the mounds served as copper workshops, while others have been identified as burial mounds after the remains of over 250 skeletons were unearthed! The site also shows remnants of a Woodhenge (similar to Stonehenge in England) that aligned with solstices and equinoxes, revealing how advanced the Cahokian city once was. Some estimates predict that 40,000 people once lived in this massive city during the 13th century…a population that would not be seen again in America until the 18th century!