Evolution of the consideration of green corridors in the planning: the case of Madrid

River corridors treatment in Spanish planning instruments has evolved since its considerations as limits or barriers to urban growth (s. XIX), to see them as places for recreation activities (1920.60) or opportunity areas for urban and industrial development (1960-80), to currently consider them as spaces to protect from urban extension. The evaluation of Spanish historical experience in planning has shown the ineffectiveness of conventional planning politics.  Even, current protectionism could be a severe limitation to develop the potential metropolitan roll of river corridors, due to its segregation effects from urban areas and the difficulties of applying planning techniques on land acquisition to these spaces.