There are at least four river valley civilizations that developed around the world.  This was the place where sedentary life began, where farming began, that started the agricultural revolution that changed the world forever.  Over thousands of years a new way of life developed in Mesopotamia which means land between the rivers, the Tigris and the Euphrates.  This same type of life was developing in Africa along the Nile River, and in India and China in the Indus River Valley and the Yellow River Valley.