The research and teaching project GREEN DENSITY focuses on the sector of Waldstadt, a strip of forest bordering the city of Bern and separated from the Bremgarten forest by the highway. This field of investigation is particularly adapted to explore the above-mentioned stakes. The process includes the elaboration of six visions from students’ projects developed within Prof. Emmanuel Rey’s workshop. Through complementary approaches, they aim at experimenting, comparing and assessing diverse possible urban forms for the development of such a site. In a context of reconsideration of urban sprawl, sites likely to host new inhabitants and jobs close to public transport are becoming highly strategic. Indeed, their densification allows the realization of new mixed neighborhoods, inscribed as part of a broader sustainability perspective. Thematic insights are intertwined with the six visions. Coming from experts from diverse disciplines and horizons, these contributions present the environmental, energetic, sociologic or economic issues raised by the creation of such a neighborhood.