Mexican metropolises, like many others in Latin America, are facing complex challenges connected to rapid urbanisation and population growth. Local governments struggle to provide the necessary infrastructure, housing, security, and basic services in a highly divided—socially and spatially—urban realm. Socio-spatial fragmentation in cities like Guadalajara and Puebla has existed since their foundations in the 16th century, as planning guidelines in the <em>Laws of the Indies</em> established differentiated rules for Spaniards and indigenous people. However, in recent decades, neoliberal planning and housing policy reforms, the consolidation of the real estate market, growing crime and violence, and socioeconomic disparities have contributed to more tangible forms of planned socio-spatial fragmentation, such as gated communities. This work discusses how policies and social practices have led to the normalisation of these fortified enclaves in the metropolises of Guadalajara and Puebla, whose capital cities are preparing to celebrate their 500th anniversaries in a context of conflict, loss of shared space, insecurity, and social inequalities. The work is based on a comprehensive review of national and local planning and housing policies, a historical and cartographic analysis of neighbourhood development, and qualitative research in Puebla over a decade, along with similar work in Guadalajara in the last couple of years. The relevance of this work lies in identifying the role of planning in the production of fragmented urban structures and visualising the possibilities for more inclusive solutions.