The people who built and occupied the prehistoric village of Aztalan, ca. A.D. 1100 - 1250, replicated major features found at the much larger Middle Mississippian site of Cahokia near modern day St. Louis. An outer stockade with bastions surrounded the twenty-two acre enclosure, with two additional stockade systems inside the enclosure, though it is not known if all of these walls were standing at the same time. Additional mounds and other prehistoric earthworks are located east of the Crawfish River. The Southwest Platform Mound, the site's largest and principal mound, was not a burial mound, but did have a large structure on its summit that was likely used for communal ritual activities. The Northwest Platform Mound is associated with numerous burials. To the northwest and outside of the stockade is a line of several conical, circular-shaped mounds built to commemorate important events; this line once extended well to the north and includes the "Princess Mound," located behind the historic structures just north of the park, which contained the remains of a young woman covered in thousands of shell beads. The Northeast Platform Mound, originally no more than five feet high, has been greatly reduced by cultivation and is today visible only as a slight rise marking the mound's southern edge. The Southeast Mound, often referred to as the "Gravel Knoll," has been shown to be a small glacial kame modified by Aztalan's inhabitants to resemble a platform mound.