If we look at them in the light of sustainable development, these archiborescent projects are not intended to destroy our existing heritage. On the contrary, they symbolise the integration of new thinking into the city’s history and into the continuous chain of change which has marked its evolution. The addition of external envelopes and grafts taking the form of structures which are either vegetal or made from biomimetic materials into existing buildings is intended to encourage the transmission of the idea of a necessary change in the functioning of the habitat and of consumer habits. These representations of adjoining houses, each on its own plot with a 6-metre facade, typical of Brussels, centre our reflection on the very city where the first Vegetal City exhibition is taking place. They confront the visitors with a vision of a possible alternative reality for the familiar places in which they live. New pedestrian routes are being developed among the roof gardens which spread throughout the city. Linked to one another by lightweight footbridges, they allow people to stroll through a space in which their view is not blocked by the built-up fronts of the buildings which face onto the streets – where they can see the sky and the horizon, as well as the cityscape of the roofs and gardens.