Urban leftover spaces tend to be integrated into urban strategy as an opportunity to prefigure the city of the future. Public decision makers are now encouraging inhabitants to take ownership of these spaces. On the model of the traditional agricultural fallow, which consists in working the land to prepare for future crops, we introduce the notion of urban fallow to qualify these spaces made available to the initiatives of local players to develop a transitional project. In any complex system, it is the sub-systems, through their diversity and capacity for creation/innovation, that give the whole (the system) a capacity for adaptation, enabling it to re-produce itself over time. It is thus at the level of its neighborhoods (of its sub-systems) that the city will draw the springs of its resilience. Urban fallows will enable the innovative and experimental capacities present in neighborhoods to express themselves in temporary projects. The aim of urban fallows is to take targeted action on specific points and locations in the area, in order to extend its effects and ultimately respond more broadly to problems diagnosed on the wider scale of the district. Five main issues that will guide the nature of the projects to be prioritized on these urban fallow lands: 1) enhancing and restoring an identity to the site, 2) revitalizing social and cultural life, 3) improving biodiversity and the quality of life, 4) revitalizing the local economic fabric, and 5)strengthening urban cohesion. Planned and thought out as part of an urban acupuncture strategy, these urban fallows will reinforce the dynamism of the city’s various territories and, in so doing, contribute to the city’s resilience.