The early civilizations first developed in the Fertile Crescent region of Mesopotamia between the Tigris and Euphrates Rivers. The Sumerians were among the first, establishing independent city-states in Southern Mesopotamia due to the need to irrigate farmland. They invented writing, mathematics, the wheel, and advanced architecture. However, the lack of natural defenses made Sumer vulnerable to invasion, and it was ultimately conquered by the Akkadian Empire around 2500 BCE. The Akkadians and later Babylonians adopted Sumerian culture and extended irrigation systems. King Hammurabi of Babylon created one of the first legal codes around 2000 BCE. Subsequent empires