How is Heart of Darkness a story of man's adventure?

While there are many labels that can be applied to Kurtz
and what was done to different areas of the world under colonization, there was a sense
of adventure present.  Marlow has to find Kurtz through progressing through the Congo in
order to reach his goal.  The journey to find him is both adventurous on a physical
level, as traveling down the Congo is arduous in its own right, and on an emotional
level, whereby the more Marlow learns of Kurtz, the greater the complexity in their
relationship emerges.  In terms of Kurtz himself, the things he did in the name of
"civilization" as well as the reality that there is this darker side present is one
where adventure was present.  It might not have been good adventure, but it was
adventurous nonetheless.  There might even be an argument made that Kurtz's final words
helped to spawn a great deal of intellectual adventure in terms of their meaning and
implications.