Patrimonialization places great value on significant elements of a people's past; however, their meaning is often stifled by rapid urban growth in cities and their development practices, which often become forgotten policies. This article describes some examples of how governmental institutions that dictate the declarations of Historical Monument are used as standard-bearers in the fight for local identity and how they then become viable and activist solutions to halt mega development projects in urban areas. Specifically, we will discuss the patrimonialization of two colonial forts, Nacimiento and Tucapel, both of which have great heritage value and are located the Biobio region in Chile, a country where these practices of domination and commercialization end up blurring local identities and start forming part of the discourse of the tourism industry, thus decontextualizing and stripping the sites of the real sense of Historical Monument. On the other hand, we will see how some sites emerge as antagonists of this process valued as cultural heritage because of their local identity component, inciting a fight for the defense of a common past, as in the case of the industrial cities of Lota and Tome, also located in the Biobio region.