I am fascinated by real world adventurers. Whether it is Bandeirantes in the Amazon, Cossacks exploring Siberia, fur traders in the American West, Icelanders sailing ever Westward, or ancient Chinese noblemen sailing to iron age Japan, I find the theme of men compelled by desperation or desire (probably both - presumably always both, for one reason or another?) to strike out into the unknown, or the dangerous and known, the most interesting phenomenon of human history.
What is probably the most interesting thing about it is that it is so morally complex: it is simultaneously typically both romantic and horrifying, necessary and wasteful, noble and criminal. How admirable it was of Pizarro or Cortes to do what they did - the astonishing combination of courage and leadership - and how utterly criminal and awful. They are the biggest-scale examples of the contradiction. But on the small-scale, too: the Icelanders weren't responsible for cultural vandalism or acts of genocide when they discovered Newfoundland, but they certainly made no bones about killing the 'Skraelings' they found there, and those Skraelings had homes and families; yet at the same time these Icelanders can be cast as paragons of universally recognised virtues - escapees from grinding poverty refusing to accept their lot; expanders of horizons; rebels against overweening authority; defenders of family. Individual Amazonian explorers were on the one-hand brutal disease-vectors and the forefront of what would ultimately be exploitation and destruction of natural resources on a vast scale; but on the other hand they were startlingly brave and resourceful, larger than life characters who you cannot (or at least I cannot) help but envy - who wouldn't want to explore the Amazon given the chance? Think of the original climbers of Mt Everest; little did they know that in a matter of decades their actions would inadvertently result in a sacred mountain being transformed into a rubbish tip/sewer, yet at the same time nobody sane could possibly suggest the original conquest of the mountain isn't a thrilling and inspirational tale.
I have recently been reading about Japanese mercenaries in the Dutch East India Company under the leadership of Jan Coen. Coen was apparently a great advocate of the use of Japanese mercenaries to solve manpower problems in the Company's burgeoning Asian empire. He ultimately shipped about 300 of them out to serve in various far-flung locations, and typically put them to use in the most dangerous and difficult situations - because they were such good fighters, so aggressive, and apparently willing to risk their lives where Europeans might not. What this ultimately seems to have meant is that these Japanese mercenaries were for a time at the forefront of Dutch imperialism in Indonesia, with perhaps the most notorious event being the massacre of the population of the Banda Islands in 1621. (The Spanish had similarly made use of Japanese mercenaries in the conquest of various locations in the Philippines.) This period did not last long, as the Japanese proved ultimately too aggressive to lead and eventually the Shogun issued edicts preventing anyone from journeying outside the islands, but it is interesting to see the contradictions played out there once more: this is simultaneously a tale that appalls and enthralls. An illustration of imperial brutality par excellence, and yet the idea of impoverished Japanese samurai seizing their chance to travel to distant lands in order to make something of themselves is also a story of human optimism.
No, don't worry, I'm not going to turn this into one big parallel for D&D adventuring, which is after all just a game, except to say that I think D&D encapsulates the interesting contradictions at the heart of adventure very nicely. D&D PCs tend to do appalling things. But the game itself is an embodiment of optimism: be bold and be somebody. There is no reason why this should have any impact on how the game is played, but it is interesting to reflect on.