ABSTRACT
At the scale of the built-up area, a neighbourhood is an urban fragment: although its internal complexity is generally great, its functions and the way it operates are dominated by its interaction with the rest of the built-up area, or in other words with its metropolitan context. The context’s influence and domination are achieved through the built-up area’s territorial extension both in space and as a set of activities, as an urban mass of inhabitants and jobs: this mass puts pressure on the neighbourhood to contain, on a local level, urban functions, inhabitants, jobs, and various amenities (e.g. services, shops, green areas). In addition, the urban mass in space, in order to operate locally and globally, equips itself with major resources: dense built areas to use the land efficiently (cf. building height), high-capacity transport networks such as express roads and in particular rail lines for public transport. These major resources affect the local level; they determine the operation of the neighbourhood that must deal with them: the situation in relation to major facilities, clusters or the most intense urban hubs and in relation to modes of transport that provide accessibility, conditions the contents of the neighbourhood and its own facilities with a local scope. Lastly, the geographical influences that are salient at a given time have taken form gradually: the weightiest facilities involve long-term investments, creating significant inertia in the built-up area and making planning incremental. To sum up, the fundamental coupling of a neighbourhood with its metropolitan context occurs when it is at one with the built-up area, as a receptacle of activities and a user but also a bearer of major facilities. Planning can add more elaborate couplings, like specialization in certain functions – cf. the scientific vocation assigned to Cité Descartes. This kind of specialization makes the neighbourhood attractive to the activities concerned, and its attraction will be all the greater in scope and intensity if the whole built-up area contributes with its mass that generates flows, transport facilities to channel the flows, and an arrangement of similar polarities: this is the notion of a marketplace, a feeding and catchment area.
