This thesis considers the architectural potential of hidden hydraulic systems and the cycle of water within cities with a view to acknowledging water’s invisible, yet essential movements through an urban area. A combined sewage system dating from the late 19th century in older parts of Ottawa causes untreated wastewater to be discharged directly into the river at sixteen locations. Architecture at the Outfalls proposes the design of sixteen habitable spaces at these locations to materialize the collision of hidden hydraulic infrastructures and everyday paths, and engineering systems and the public realm. The architectural interventions also reveal water as an essential resource for living, and the Ottawa River as a visible, topographical, and spatial element in urban life.