This thesis analyses the mutual relations of production between the open spaces and the double core metropolitan region created through the proximity of Valparaiso and Santiago de Chile. Given that Chile has been facing strong urban pressure since the 1970s, the existence of numerous open spaces of various sizes, that are lightly built and with mostly low land use, as close as 20 km from the two urban centres in this emerging country, may indeed appear paradoxical. Nevertheless, the process of metropolitization is dependant upon these open spaces for growth and, conversely, in order to exist, these open spaces need the infrastructures, stakeholders, and laws of these metropolitan areas. This study adopts a social geography approach, inspired by the work of Henri Lefebvre and is based on a long-term field study of three geographical areas. Each area is part of the third urban ring of Santiago and focuses on a distinct type of geography (including a coastal area, a mid-mountain area, and a part of the central basin). The research adopts a mixed methodological approach to capture the tri-dimensionality - conceived, lived and perceived - of the open spaces in relation to metropolitization.Though marginal and diverse, these open spaces remain strategic for metropolitization, which explains both the conflicts that they generate as well as the need for local authorities to incorporate them in their plans for urban development
