The ancient North American city of Cahokia had as its focal point a feature now known as Monks Mound, a giant earthwork surrounded on its north, south, east and west by large rectangular open areas. These flat zones, called plazas by archaeologists since the early 1960s, were thought to serve as communal areas that served the many mounds and structures of the city.

New paleoenvironmental analyses of the north plaza suggest it was almost always underwater, calling into question earlier interpretations of the north plaza’s role in Cahokian society. The study is reported in the journal World Archaeology.