The management of natural heritage is one of the primary aspects in the field of urban and regional planning. From the establishment of hygienist parks in early twentieth-century industrial cities to the delineation of protected landscape units at the regional level, innovation in the techniques of regulation and conception of open spaces has undergone a drastic change in the last three decades. The purpose of this study is to characterize how environmental paradigms are incorporated into supralocal planning, emphasizing the conceptualization and regulation of open spaces, through a comparative case study of three supralocal plans in Bologna. This research is based on qualitative methods. The analysis of the plans studied reveals a convergence in concern for the preservation of cultural heritage, the delineation of landscape units, and the regulation of natural and landscape resources. However, differences are identified in the trends in the conceptualization and representation of open spaces, transitioning from static approaches to more dynamic perspectives. These findings underscore the importance of adapting planning strategies to specific contexts, promoting coordination between different levels of government and actors, and considering the natural and cultural aspects of the territory comprehensively for sustainable and equitable development.