Mesopotamia is the region of the Tigress and Euphrates rivers in what is now Syria and Iraq.  It is where the world’s oldest civilizations were founded after the invention of agriculture with the growing and storing of grains like wheat, millet and barley.  They developed irrigation, writing, the wheel, and codes of law including legal contracts.  The civilization was prosperous for three thousand years, but it started to decline at about 2,350 BC due to declining crops from desertification, among other reasons such as the rise of iron metallurgy which was a resource that did not exist in that area.