Large-scale design -’ Mobility interface models and urban transformation strategies This research project is based on the hypothesis that the urban transformations generated by mobility interfaces constitute a key component of successful sustainable urban development. Effectively visioning and understanding these multimodal interchange hubs must therefore become a major strategic objective, in order to conceive an urban model that is compact - and networked and intelligent. With this aim in mind, this research aims to propose innovative strategies for transforming these communication interfaces into central reference points within the contemporary metropolitan landscape. Projects of this kind have already been designed and realised in most major European cities during the second half of the 20th century. These designs, characterised by their complexity and scale, formed the starting point of the major railway stations in today's cities, incorporating different forms of mobility over the course of time. Today they appear not just detached from their urban contexts - the very contexts in which they are embedded - but also unable to meet the current demand for functional mixity and communication effectively. They are undergoing obsolescence and finding it difficult to adapt to the paradigm shifts that have intervened - socially, economically and spatially. At a time when the city can no longer be conceived exclusively in terms of ex-nihilo construction, but must be viewed in terms of transforming an existing built fabric, what future can be proposed for these existing transport interfaces? What strategies can be developed to anchor them in their surrounding urban context? What capacity do they have for hosting new activities, new public and private spaces? Finally, what forms is it possible to imagine for this kind of design? Three hypotheses emerge: the development of mobility interfaces has generated specific architectural and urban forms correlating to the evolution of mobility forms themselves; the transformation and obsolescence phases of mobility interfaces offer potentials for metropolitan regeneration; and the process of producing a complex design calls for articulation and interrelation between different architectural and urban scales. To verify these hypotheses, the first part of this thesis is focused on the comprehension and analysis of these multimodal hubs, based on a review of architectural and urban theories that address the issue of how major urban projects relate to transport infrastructures. This is followed by close analysis of a series of relevant case studies within the Paris metropolitan area. The second part of the thesis proposes design tools to generate new urban and architectural design processes, derived from a process of design-based research. The final part of the thesis aims to demonstrate that this type of intervention is a design project with its own specific scale and complexity: between large building and urban fragment.