Early civilizations used to develop throughout river valleys so the fertile soils could allow the progress and success of agriculture.
Mesoponamia for example was developed between the Euphrates and Tigris rivers, both fed by many affluents; such river system drained the region set up by highlands which made it very fertile and sometimes unpredictable, but had rich soil suitable for abundant crops thanks to the seasonal rains or annual floods, thus settlers benefited from farming and the minerals from the mountains; the region also had marshes and plains.
