The knowledge that societies have of their geological environment and of the materials used in their heritage is of great importance for the sustainable use and conservation of traditional natural stone architecture. Similar weathering mechanisms occur in natural environments and the built environment and, in both cases, weathering may endanger both natural and built heritage. The Sierra de Guadarrama (Spanish Central System) is a privileged area in which natural and built heritage coexist. This paper describes an area of particular monumental and geological interest on the northern slopes of the Sierra de Guadarrama; its main aim is to propose an itinerary for members of the public, presented as a route through the area around Segovia, in which architecture/cultural heritage and an Earth sciences approach are brought together with an educational purpose. To this end, some connections are established between weathering forms in natural and built environments, as well as between the lithological characteristics of the rocks used in construction of ancient monuments in the area and the distribution of stresses and loads of walls.