"Nearly every major city was built near the convergence of many rivers. As cities grew with the Industrial Revolution, these rivers became conduits for disease and pollution. The 19th-century solution was to bury them underground and merge them with the sewer systems. These rivers still run through today's metropolises, but they do so out of sight. [This film] examines hidden waterways in cities around the world and introduces us to people dedicated to exploring and exposing them"--Container.