Mesopotamia, located between the Tigris and Euphrates Rivers in modern-day Iraq, was the site of some of the earliest human civilizations. Sumerians settled there around 3500 BCE and developed innovations like irrigation systems, the wheel, writing in the form of cuneiform script, and the concept of cities with religious temples called ziggurats. Subsequent civilizations like the Akkadians, Babylonians, and Assyrians expanded on these foundations, with the Babylonians instituting an influential legal code under King Hammurabi. Though power shifted between groups, Mesopotamia represented the birthplace of many cultural advances that shaped later societies.