Preserving water resources in urban areas is a major challenge for the future in Europe. High urbanization and drought have caused groundwater levels to drop dramatically in many places. Rainwater cannot easily sink into the natural soil and maintain the groundwater level. Before the water finally infiltrates the soil or flows into lakes and rivers, the rainwater has already been polluted with harmful waste from urban areas. The result is a disruption of the natural hydrological cycle. Maison L’eau proposes an alternative hydrological cycle, which is part of a sustainable approach to architecture and urbanism. This new hydrological cycle is based on a range of solutions, from rainwater collection and runoff, using natural filtration with plants, to further processing that makes the water potable and ready for storage and further distribution. This completely new water purification process comes to life through the creation of a recreational and educational landscape aimed at an “awareness process” that informs the public about the importance of water. The water house in which the naturally treated water is stored is inspired by the structural concepts and the spatial organization of the water castles of François Hennebique, a Belgian architect from the 20th century. Many of these types of water castles can still be found in the north of France and the south of Belgium. In the elaboration of Maison L’eau, the balance between architecture, the building, the landscape, architects and the hydrologist is crucial.