Currently, in a context of crisis, there is a growing trend towards a return to the past. This is not seen in a strictly analytical and historical perspective, but rather as a nostalgic collective mental construction of a reality that would never have existed.In fact, cities are undergoing a de-densification process in a rhizomatic and spontaneous perspective, and urban voids arise at random, both in the center and in the periphery. This doctoral thesis will have a conceptual and historiographic investigation on rehabilitation and patrimony. The second part will focus on some operational strategies for urban development in historic centers, especially in small and medium-sized cities.