"In fact, since the originary enclosures, the concept of boundary has undergone numerous changes as regards both the facade and the neighbourhood it fronts. From the palisade to the screen, by way of ramparts, the boundary-surface has recorded innumerable perceptible transformations, of which the latest is probably that of the interface. Once again, we have to approach the question of access to the city in a new manner. For example, does the metropolis possess its own facade? At which moment does the city show its face?