Except if you plan to build an underground city, people still have to walk from/to the metro station to/from wherever they live or work. And people also still s

Except if you plan to build an underground city, people still have to walk from/to the metro station to/from wherever they live or work. And people also still strangely favor having a bit of sunlight. As a French living now in Canada, Paris streets are narrow in general, and especially the sidewalks are ridiculous, most of the space is for cars. One of the first thing to do would be to reclaim that street space for pedestrians and cyclists, which is an ongoing, slow and painful battle.