Sloping sites are especially appealing for habitat due to climatic, safety, or landscape factors. These benefits, which compensate for the construction effort required to build in such areas, have favored the urbanization of the hillsides throughout history. With the rise of private cars, the accessibility of urban hills has increased, mostly leading to a loose colonization by detached and privileged houses. At a time of climate emergency, the continuation of urban sprawl is strongly questioned. Urban regeneration projects aimed at increasing housing density, with other functions close to public transport, are among the responses provided today in Switzerland. However, these projects often face the residential preferences of the population that are not very favorable to density and are increasingly being rejected. Therefore, this research considers hillsides as a contextual specificity of Swiss cities capable of responding to the urgent housing crisis while offering housing diversification with high habitability qualities. Because slope is a condition that extends beyond the Alps, the study area of this research encompasses the perimeters formed by Swiss urban territories. Their sloping sites with good accessibility have the potential to respond to a low-carbon perspective while offering a new perception of housing typologies. The paper aims to demonstrate the quantitative and qualitative potential of sloping sites using prospective cartography on the scale of one agglomeration taken as a case study. This cartography will follow three phases: 1. Surveying the public transport network on the hillsides, taking former lines (historical concessions) and current lines. 2. Identifying already urbanized sloping sites connected to this mobility network. 3. Site potential classification. This unprecedented cartography aims to demonstrate that the hillsides of the agglomerations could be a reservoir of polycentric, decarbonized, and adapted densification projects, contributing differently to the urgent need for quality future habitats. 1. Housing crisis, density challenge, and the opportunity of sloping sites Switzerland faces a significant housing crisis with historically low vacancy rates, partly due to substantial population growth (1). The usual response to this crisis focuses on intense inward densification, generally in coordination with public transit. Indeed, to prevent the negative impacts of urban sprawl on landscapes, Swiss people voted in 2014 for the revised Swiss Federal Spatial Planning Act, which promotes densification within already urbanized sectors