What is the setting of Heart of Darkness?

The novel takes place in the 1890s and begins on a boat sitting in the River Thames, which leads from London to the sea, waiting for the tide to turn. Marlow's story takes the reader briefly onto the European continent (Belgium) and then deep into Africa by means of a trip up the Congo River to what was then called the Belgian Congo, and back to Europe again The Congo is described as a place of intense mystery whose stifling heat, whispering sounds, and strange shifts of light and darkness place the foreigner in a kind of trance which produces fundamental changes in the brain, causing acts that range from the merely bizarre to the most extreme and irrational violence.