More than 25 percent of the world’s population—that’s more than 2 billion people—do not have access to basic sanitation. That’s an astonishing number when you consider that some of the earliest sewage systems were already developed in Mesopotamia by the middle of the third millennium B.C.E.
Although not the oldest sewage system in the world—earlier drainage systems are known from the ancient Near East and across Asia and the Mediterranean—Rome’s Cloaca Maxima (meaning “greatest sewer” in Latin) is a marvel of engineering. Constructed as early as the sixth century B.C.E., this sewage system was built to drain the marshy lands surrounding the hills of the Eternal City. In later centuries, the system was enclosed, or covered, and by the Imperial period, it also included connections for public baths and lavatories. The Cloaca Maxima has remained in continuous use since its original construction. Even today, drainage water flows through the ancient tunnels.