This dissertation aims at exploring on the diffusion of sustainability in France and its role in urban and large-scale design. To this aim, the arising of sustainable urban development is regarded as a set of problems, rather than a set of solutions. Our critical position allows us to challenge the notion of sustainability from a viewpoint that is profoundly linked to reflection and practice of the large-scale project; we therefore have focused on disciplinary cultures, particularly those concerning design and planning stakeholders. The notion of figure, the issue of its consistency and relevance has allowed us to put into perspective contemporary topics, especially referring to the Italian debate on tools of design thinking. Concerning the Strasbourg case-study, our research suggests that the "sustainable metropolis" is changing meanings and relationships between different figures operating in its territory and its representations, as well as its narratives.