Worldwide urbanization brings seemingly inescapable and uncontrollable forms of densification with it. Increasingly, cities are no longer defined by clearly visible borders. Instead they form open territories that are honeycombed with infrastructures and immaterial networks. This development requires a new understanding of density: density is not the product of piling square feet on top of one another, instead it is the result of vital connections between the different urban levels. Apart from a physical and economical dimension, density also has a social significance in particular, as a means of promoting and structuring human relations and therefore contributing to a good urban life.0'Density, Architecture, and Territory' puts forward a model of density as a tool for sustainable urban development. Based on five European urban planning projects in Saintes, Utrecht, Copenhagen, Nantes, and Bregenz, various densification strategies are presented and analyzed. Discussions with the architect Kees Christiaanse, the philosopher Marc Armengaud, the landscape architect Henri Bava, and the economist Allain Sallez round off the publication.