This research approach the phenomenon of informal neighborhoods in nature reserve areas, particularly in what the Bogotá Land Use Plan defines as a Mountain District Ecological Park. For this reason, this work deals with a specific neighborhood, called San Germán, which is located within Parque Entrenubes, which, in turn, is located in the southeast of the capital. A neighborhood without legal clarity in its legalization and with multiple socio-environmental problems. In this sense, this research is presented as a useful case study to understand some characteristics of informal neighborhoods, their history, their socio-environmental impacts, and the alternatives offered by sustainable occupation models for this type of neighborhoods.