The Sumerians settled on the fiat, fertile plain built up over thousands of years by alluvial deposits from the Euphrates and Tigris flowing southwards into the Persian Gulf.

• 幼发拉底河和底格里斯河由北向南流入波斯湾，经过几千年的沉积，沿途形成了肥沃的平原，苏美尔人便在两河流域定居下来。