The river symbolizes the journey that, in this novel, mankind takes on his way to the dark side – to his heart of darkness. The Congo allows Europeans to journey to the center of Africa without having to really enter the land. The river runs through Africa, so the white man can journey on the river and still remain outside of the real Africa. As Marlow travels up the Congo on his journey to find Kurtz, he can observe things that are happening on the land without having to get involved in them. He represents the Europeans who bring their culture to Africa and stand by and watch as it destroys them. The horrors that Marlow observes when he finally finds Kurtz are unspeakable. They represent the worst side of humanity, the evil that exists within the human heart, the heart of darkness. This is why Kurtz screams out on his death bed, “The horror! The horror!” Perhaps God lets him see for one brief moment, all the severed heads of the people he tortured and killed, right before plunging Kurtz into the ultimate darkness of hell.
The Congo also represents Africa. The river does not want the Europeans in Africa, so it makes the journey difficult going into the country, but easy going the other way. The water flows quickly downstream taking the white man out of Africa, but slowly on the way into Africa. When Marlow is going up the river to find Kurtz, he struggles not only with the river, but with trying to figure out the challenges that lay before him. On the way out, both things are easier.