Bordeaux embodies the traditional European heritage city. Like many cities on the old continent, it is a palimpsest that has witnessed several currents of thought on urban development patterns, comfort, modernity and ecological awareness. Today, the city comprises several urban elements reflecting these diverse perspectives as well as major societal changes that are transforming our understanding of these testaments of the past. This chapter aims to explore the debates and periods of rehabilitation, both moral and physical, that have successively affected multifunctional districts. These districts, encompassing both traditional neighbourhoods (from the eighteenth and nineteenth centuries) and modern neighbourhoods, are now confronting the challenges of ecological transition. By elucidating the principles that governed the construction of these neighbourhoods, subsequent viewpoints, particularly those of the modern movement, and contemporary perspectives, we will demonstrate their significance in current discourses and their alignment with the goals of creating sustainable cities in the twenty-first century. This chapter shares the results of a two-year joint research programme (2017–2019) conducted by the PAVE and GRECCAU Research Centres (ENSAPBx) and the University of Cincinnati (DAAP). The project focused on the perceptions of stakeholders—inhabitants, landlords and experts—of what constitutes sustainable heritage in the context of the energy transition with regard to modern housing. The research entailed stakeholder interviews, housing measurements (including hygrothermal and natural light assessments) and socio-spatial analyses, focusing on the modern neighbourhoods of Meriadeck and Pontet-Lamartine. These two neighbourhoods, despite their contrasting dimensions, typologies and locations, share urban qualities and a strong potential for change. Meriadeck (1951–1980), in the centre of Bordeaux, is characterised by deck-and-tower structures with separate circulation systems and crossshaped towers overlooking one of France’s first protected heritage areas. Pontet-Lamartine consists of twenty-eight patio row houses (1970–1971). The owner-residents of this neighbourhood are proactive in promoting their Modernist heritage and developing civic life, for example, joining forces to safeguard amenities like shops, services, shared public spaces and a park open to a rapidly densifying surrounding area. In sharp contrast with their environment, these two neighbourhoods recently merged with the traditional city centre and the suburban fabric of the growing metropolis. Both have contributed to Bordeaux’s sustainability through their distinctive designs and facilities. This chapter first discusses the spatial and urban qualities of the traditional stone city and modern post-war neighbourhoods, as envisioned by their designers, which can be described as sustainable today. Combining both objective metrics and subjective evaluations, this research identifies specific urban features in these districts that, rather than confirming their obsolescence, demonstrate the value of these areas in terms of quality of use. It argues for an adapted definition of the sustainability goals and strategies in heritage neighbourhoods dating from and before the twenty-first century. Finally, we highlight the inhabitants’ commitment to achieving the physical and moral rehabilitation of the heritage they value while addressing the challenges of sustainability on a metropolitan scale.