The ancient civilization that developed in Mesopotamia is known as Sumer. Located in the region between the Tigris and Euphrates rivers, Sumer is recognized as one of the world's earliest urban civilizations, flourishing around 4500–1900 BCE. The Sumerians are credited with developing one of the first forms of writing, cuneiform, as well as significant advances in agriculture, mathematics, and astronomy. Their city-states, such as Ur and Uruk, established complex societies with governing systems and monumental architecture, contributing immensely to human history and culture.