This civilization flourished along three rivers, the Fortaleza, the Pativilca, and the Supe. These river valleys each have large clusters of sites. Further south, there are several associated sites along the Huaura River. The alternative name, Caral-Supe, is derived from the city of Caral in the Supe Valley, a large and well-studied Norte Chico site. Complex society in Norte Chico arose a millennium after Sumer in Mesopotamia, was contemporaneous with the Egyptian pyramids, and predated the Mesoamerican Olmec by nearly two millennia.