The Sumer civilization thrived in ancient Mesopotamia between the Tigris and Euphrates Rivers in modern-day Iraq. It was the first civilization to develop systems of writing, government, religion, economic classes, advanced architecture like ziggurats, science, arts, and literature such as the Epic of Gilgamesh. The Sumerians invented innovations like the wheel, plow, calendar, bronze metallurgy, silver currency, and the first written legal code. However, rivalry among Sumerian city-states led to decline, and the Akkadian Empire later conquered and unified the region under rulers like Sargon I.