Eridu is one of the oldest known cities in ancient Mesopotamia, located in present-day Iraq. It is believed to have been founded around 5400 BCE and is often considered the first city in human history. Eridu was a significant religious center, dedicated to the water god Enki, and featured a large temple complex. The city is known for its unique architecture, including mud-brick structures and ziggurats. Archaeological excavations have revealed layers of habitation, showcasing the development of urban life over thousands of years. Eridu's influence extended throughout the region, contributing to the rise of other cities in Sumer.