The modern and contemporary city has given birth to vast peripheries due to rapid growth. A first glance at these areas reveals that architectural theories and urbanism paradigms encounter each other without fixed rules or regulated planning. Moreover, these sectors located close to city centers are often still considered as lifeless and without interest, even by building professionals, despite an intense debate on the topic since the 1960's. Nevertheless, it seems appropriate to explore in greater detail the question of this suburban phenomenon. These areas provide numerous advantages, giving the opportunity to enjoy the proximity of the city centers and its corollaries (jobs, culture, mobility, education, leisure activities) without living in dense and saturated places like those in urban centers. In the first section, the dissertation explains the historic and present evolution of the periphery, as well as new forms of urbanization over the last fifty years. A case study explores the evolution of perceptions on the periphery from distinct architects and theoreticians from the 1960's until today, leading to a new critical vision (Aldo Rossi, Robert Venturi & Denise Scott Brown, Rolf Keller, Rem Koolhaas, Stefano Boeri, Mirko Zardini). In the second section, the dissertation regards the vast debate on sustainable development by analyzing the densification possibilities of the periphery and the compatibility of preserving its characteristics, such as building and lifestyle heterogeneity, landscape qualities, and the permeability between building complexes. This offers lower density than city centers, which provides an alternative to peri-urban urbanization and, consequently, a contrast to sustainable development. A case study of three Swiss agglomerations analyzes the innovative strategies in current urban planning initiatives (Lausanne, Lugano, and Zurich). In the final section, the dissertation investigates collective housing in peripheries that are currently increasing their density. Therefore, the present debate is examined by accentuating the questions of collective housing within the context of suburban development. A case study is dedicated to the architectural specificities of this topic, analyzing a corpus of six residential complexes built or being planned since 2000 (Les Carolins/Bachelard-Geser, Sunnige Hof/Burkhalter+Sumi, Katzenbach/Zita Cotti, Leimbach/Galli-Rudolf, Triemli/von Ballmoos-Krucker, Burriweg/Frank Zierau). This architectural case study is conducted with not only typological and morphological tools, but also perceptive ones.