For several years, Europe has been involved by an active debate on directions and tools for the sustainable urban development. Recent urban policies within the European Community have mainly based around actions of transformation, regeneration, construction over and inside the built environment; however, it is now impossible to delay a turnaround concerning settlement attitudes and the awareness toward the need for an all-round ecologically responsible behaviour has increased. Many studies focus on interactions between density and nature and examine the concept of density, on its measurement and limits. In France, in fact, Jean-Michel Léger and Béatrice Mariolle are carrying out research on the intermediate areas between cityside and countryside, comparing densification scenarios with new low-density models that seek a connection with farmlands. Paola Viganò’s proposals for interventions on French and Belgian areas highlight strong contradictions hidden in the compact city model and show how urban growth and degrowth no longer express a collective project of redistribution of resources and opportunities; rather, they represent the result of a clash between financial capitals, taking place in the form of concentration and polarization projects. The essays and the projects presented in this issue fit into this debate and share significant considerations, through experiences carried out in contexts such as France, Germany, Switzerland and Luxembourg.