Gothic literature is always concerned with the duality of society and reflects the anxieties simmering beneath the surface. Never is this more true than in the fin de siecle Gothic classics: Stoker's Dracula, Wilde's Picture of Dorian Gray, and Stephenson's Dr Jekyll and Mr Hyde, all of which are concerned with the idea that the politeness of late Victorian society is only a veneer, beneath which society is dark and ugly. Dorian Gray, like Jekyll and Hyde, is set in London, a city which serves to represent a whole sprawling empire. London, in this novel, is a microcosm of society as a whole: Dorian moves between the respectable London of the upper class, and the back-alley London that is, perhaps, more the "real" London, representing the fact that the image society portrays of itself is not necessarily the truth. Wilde debated this concern of illusion and reality repeatedly: "Man is least himself when he talks in his own person. Give him a mask, and he will tell you the truth." In the darkness, and with his evil deeds confined to the portrait hidden in the attic, Dorian feels free to do whatever he likes—and that way lies only evil.

Note as well that this novel was published in 1890, a mere two years after the height of the Jack the Ripper murders in London. The imagery of dark alleys and "black-shadowed archways" recalls the lurid details published in newspapers and magazines the world over of prostitutes killed gruesomely in London's underworld—but, indeed, in Whitehall, only a stone's throw from some of the city's most respectable districts. The importance of the setting in this novel, then, is that it reminds us that the best and worst of society often go side by side and, indeed, are frequently contained within the same person.

You might like to consider how the city of London is presented and how it becomes a reflection of Dorian's somewhat divided character in the story. We appear to be presented with two areas of London. There is the socially acceptable area, in which Dorian dwells with his friends, Basil and Lord Henry, and then there are the parts of London where Dorian indulges in his illicit vices, such as opium dens, brothels and other places. However, these two halves of London seem to suggest the way that Dorian is able to present a face of innocence and purity to the world on the one hand, whilst at the same time engaging in ever more decadent acts that spur on his own corruption. Note how we are first introduced to this darker side of London after Dorian breaks up with Sybil Vane:

Where he went he hardly knew. He remembered wandering through dimly lit streets, past gaunt, black-shadowed archways and evil-looking houses. Women with hoarse voices and harsh laughter had called after him. Drunkards had reeled by cursing, and chattering to themselves like monstrous apes. He had seen grotesque children huddled upon doorsteps, and heard shrieks and oaths from gloomy courts.

It is highly significant that after this act of destroying Sybil Vane, that arguably sets him on the path of corruption, Dorian discovers the darker side of London. Note how the description in the above paragraph gives this side of London an evil, dark and oppressive feeling, with its "black-shadowed archways" and "grotesque children" and "gloomy courts." Clearly this is a Gothic setting that hints at the division within the character of Dorian himself. From this point onwards in the book his life is spent divided between the "dark side" of London and the respectable side.