In front of the dangers of the planetary urbanization, realistic proposals of existential ecology respectful of the cultural diversity, the range of the beliefs and rites, the incredible difference of the temporalities which govern and animate the life of each homo urbanus of the planet. A test filled with amazing stories drawn from a long curious experience of the "urban thing", in its many territorial forms, by one of the best specialists in the field. At the beginning of this century, one thing is clear: urbanization is global. A standard of living, more or less homogeneous, is spreading everywhere, with its attendant consumption norms, standard behaviors, collective values ​​and individual practices that unbalance ecosystems. It is this revolution with paradoxical expressions that Thierry Paquot explores here in his multiple territorial forms - slum, megalopolis, secure residential enclave, average city, global city, urban diffuse ... The author points the challenges to be met: the "good "land use in the face of the extension of urban areas and the reduction of agricultural land; the "good" way to move, in a world facing the probable shortage of oil and the multiplication of ordinary mobilities (mass tourism, shopping, sports practices ...); the "good" way to ensure to everyone a minimal urban comfort, favoring a reasoned decrease of certain consumptions; "good" governance, which requires the invention of new democratic practices; the "good" habitability between oneself and others. Only an existential ecology respectful of cultural diversity, of the range of beliefs and rites, of the incredible difference of temporalities that govern and animate the life of homo urbanus can assure to all an urban future.