A master plan is a dynamic long-term planning document that provides a conceptual layout to guide future growth and development. Master planning is about making the connection between buildings, social settings, and their surrounding environments. A master plan includes analysis, recommendations, and proposals for a site’s population, economy, housing, transportation, community facilities, and land use. It is based on public input, surveys, planning initiatives, existing development, physical characteristics, and social and economic conditions. Master planning can assume some or all of these roles: Develop a phasing and implementation schedule and identify priorities for action Act as a framework for regeneration and attract private sector investment. Conceptualize and shape the three-dimensional urban environment. Define public, semiprivate, and private spaces and public amenities. Determine the mix of uses and their physical relationship. Engage the local community and act as builder of consensus. As city regeneration initiatives are generally long-term propositions, it is important to consider the master plan as a dynamic document that can be altered based on changing project conditions over time. For example, in the case of the Santiago repopulation program detailed in this volume, the municipal master plan was modified 29 times during the implementation phase. These changes sought to either allow for more density and height in some areas, or to restrict and lower the height of the buildings—including the definition of areas under patrimonial protection (Arraigada, Moreno, and Rovirosa 2007). This flexibility has been beneficial to the real estate sector, enabling increases in the number of floors and housing units per building. Master plans can have an important role in determining the shape of the urban environment. If not well conceived, they can lead to problems in the future. For instance, one of the criticisms of Santiago’s master plan was that it was too flexible in setting standards for beautification and building volume design. Hence, the quality of these buildings in terms of architectural design and construction materials was considered one of the weaknesses of the repopulation program (see photograph). The residents also criticized the unpleasant contrast of the high tower buildings with the existing historic urban fabric, as well as the fact that the new towers are not well integrated within the traditional neighborhoods. All of these issues could have been addressed well in advance as part of the master plan.