This text reflects on the co-production of the city as a strategy of citizen participation, reflecting both on the informal interventions (the "barriadas" identified as inner peripheries) and the semiformal ones (the "Unidades Vecianles" (Neighborhood Units) also known as UV). The system of inner peripheries has been identified in downtown Lima, comprising a series of old slums that makes up an urban entity with its own characteristics and problems. These slums were part of the northern periphery of Lima until the 1950s and extended along the course of the Rimac River, the then-border between the district of Lima and the emerging northern extension of the urban area. The "Unidades Vecianles" (Neighborhood Units) were designed "up to down," from the modernist theory of city-garden imported in the mid-20th century to Peru aimed at trying to stop the proliferation the slums on the edges of the city. The Neighborhood Units are located in Lima and there is also a participatory urban laboratory located in the city of Piura.