This work intends to address new questions posed by contemporary urban context, concerning the reactivation of use and practices within the consolidated spaces of the city: it becomes necessary to implement qualitative and social-dynamic instruments such as Intensity. The base to define and build this parameter is set through its ethymological analysis, thorugh the different interpretations about the city and the role of project in generating vitality within the urban space. This matrix of analysis is applied to New York City as a case study - chosen for its spatial conformation, its history and its social practices - selecting projects ranging across different scales, from the house to the city, thus becoming the testing ground of intensity, to investigate urban transformation and different uses of the space: a design/analysis process aiming to make intensity an operational parameter in architecture.