Paris becomes a world of unending mystery where anything is possible. This vision is fed by a typical bourgeois fascination with the disreputable, squalid, dangerous areas. Before 1914 these included the central quartier Saint-Merri, where Desnos grew up, as well as Belleville and the areas around the fortifs and the barrières (the outer gates to the city).
The Cambridge Companion to the Literature of Paris