Around the Cahokia site there are a number of paired mounds that consist of a rectangular platform mound and a conical mound. The largest pair, called the “Twin Mounds,” are at the south end of the Grand Plaza opposite Monks Mound. These two mounds are built upon a shared earthen platform. It is suggested that these mounds might be part of a mortuary complex and that a structure on top of the platform mound was probably a charnel house where the bodies of deceased were stored or prepared for burial, perhaps in the adjacent conical mound. There are four sets of these paired mounds on the site, each with different dimensions.