To call a city a slough of despond, or a great wen, or a cesspool, is to give it a functional identity, to fix it in the mind as surely as Bradley Headstone is fixed in Dickens’s novel. The city, like the people in it, lends itself to this sort of moral abstraction. Oddly enough, cities, for all their big-ness and complexity, get tagged with hard-edged images much more readily than small towns. What mental picture is conjured by, say, Chicago or Sheffield? Isn’t it more definite, more dominant, than that of Banbury? … One might add that, in England, the single feature of the city which has adhered most strongly to writers’ minds is its dirt, and dirt is one of the few objects whose moral connotation is as definite and public as its physical characteristics. The presence of dirt provides us with the elusive key we have been seeking, and the English have been quick to seize on dirt as the single defining quality of the big city.
– Jonathan Raban, Soft City (1974)