Many works use contrasting places to represent opposing forces. Conrad does this in his Heart Of Darkness, by contrasting Europe and Africa. Conrad uses this contrast to enhance the theme of innate evil and every man.
Conrad makes Africa seem mysterious to symbolize the uncivilized and barbaric nature of man. the jungle is a dark and dangerous place and the natives are seen as just barely human by the Europeans. In contrast Europe is seen as a utopian society, there are the cultured people .
When Marlow talks of London being a dark place, the theme of civilisation versus savagery comes into play. Marlow's aunt believes he is an emissary of light, being sent into the darkness. Marlow sees this darkness through the placing of heads on poles, for a man named Kurtz. All of this makes Marlow change his inner feelings of himself, which relates to the theme of the journey of the inner self. Marlow talks of when the Romans first came to Britain, and how they had actually brought some light into the sombreness of London, and how one day that light may disappear. This relates to the theme of dark and light. As Marlow tells of his voyage deeper into the unknown, his capacity for self-control is tested. Kurtz seems t