The biggest contrast in “Heart of Darkness” is the difference between light and dark. London represents the light. London is in civilization, and if London represents the light, then civilization also has a big thing to do with light. The light represents everything that everyone has learned in their life, whether it was through experiences or through other peoples mistakes. On the other side there is the darkness. Africa is the main representation of darkness. Africa was uncivilized territory that everyone wanted to explore, but the darkness frightened people. Everything that happened in the darkness, “cannibals” and “savages” prowled the darkness, awaiting travelers. Africa is the "heart of darkness".
The contrast of the Thames River and the Congo River is also big in the story. The Thames is characterized as calm. Like the light the Thames represents good. The light from London makes sure the river is seen and nothing is cryptic about the river. On the other hand, the Congo is a dark, cryptic river. It is a place of evil. The contrast of these two rivers is the difference between the good and the evil, and light and dark. The Thames is peaceful and tranquil; it symbolizes light and civilization. The Congo is wild and barbaric; it symbolizes the dark and everything uncivilized and frightening.