This book can be considered as one of the first urbanism treatises in French - the term will not be admitted until 1910 - or as an essay on urban art and the quality of the city. A city is primarily an accumulation of streets, places of circulation and exchange. Without active street (we say "alive") a city is dying. But everyday life on the street changes from one culture and one era to another. Gustave Kahn reconstructs the moods of Pompeii, the souks of the Arab cities, the canals of Venice or Amsterdam. He describes the festivals, fairs and exhibitions that transfigure the city and magnify it while attracting the world. He does not forget the utopias, the street-gallery imagined by Fourier, the passages sung by the loafers. He takes us into the Parisian street after Haussmann (which he does not appreciate), with his posters (Chéret, Lautrec, Mucha.), His lights, his animation. He calls for a bold architecture (Horta, Hankar, Guimard), worries about the arrival of the bicycle and the automobile, opposes the appropriate towers in New York but not the size of Paris. He believes above all in the presence of art on the sidewalks. An art for all, which poetsise the city. A pioneering book that deserves to be rediscovered both for its end-of-century charm and for the relevance and modernity of its subject. It comes from a comparative history of urban planning ideas that have yet to be written.