Mesopotamia was an ancient region located between the Tigris and Euphrates rivers in modern-day Iraq. Some of the earliest known writings were discovered in the Sumerian city of Uruk, including the Epic of Gilgamesh. The first settlers of the region were the Sumerians, who established city-states with kings as leaders. They developed a system of writing known as cuneiform and engaged in irrigation using canals. Mesopotamian culture was polytheistic and believed in laws of the universe called mes. Important achievements included Hammurabi's code of laws in Babylon and the development of bricks, the wheel, and cooking with fire.