Sumer, the world's earliest known civilization, emerged in southern Mesopotamia around 5000 BCE when agriculturalists settled the fertile lands between the Tigris and Euphrates rivers. Located in present-day Iraq, this civilization developed irrigation agriculture, cuneiform writing, monumental architecture, and the first urban centers such as Eridu, Uruk, and Ur. Sumer laid the foundations for later Mesopotamian civilizations with its innovations in governance, writing, art, religion, and urban planning.