Many people like to travel, myself included, and if travel has to be just one thing, it is adventure. Most people would agree that travel is a type of adventure. But, how is it adventurous? We all have googles, tripadvisors and lonely planets falling out of our eyeballs. We know in advance exactly what we want to do and when we want to do it. Is that really adventure? On the other hand, if we take a trip that is unstructured and unplanned, we tend not to stumble across those amazing things we were hoping to find (although perhaps sometimes we do). So, where is the adventure to be found?
First things first, we have to decide what we mean by adventure. It turns out that the adventure has a strong structure, consistent throughout the accounts we have recorded through history in literature and the arts . As narratives, these give us nice and simplified, but overall still somehow truthful, prototypical adventures. In each, the first act is first some kind of trigger, or "call to adventure". The protagonist (adventurer) must accept this call, or at least be somehow bundled along by it (think of Alice falling down the rabbit hole). The main part of the story is the experiences that the adventurer must go through once they have crossed the threshold. Once they have left their mundane everyday existence, they enter into a different world - we are talking about an entirely different psychic world here. From this point forward they experience only unfamiliar experiences. They are entirely disconnected from what was before. They must take some risks and they must face some challenges, whose nature may vary widely. These challenges may or may not entail some suffering, but it is crucial that the adventurer must be forced to call on some hidden resources (e.g. of strength/resourcefulness/guile). When the adventure has ended (as adventures must) the adventurer must return to the "normal" world. But this is not the same world that they had left behind. Our adventurer's psychic world has shifted, and so must the real world shift to accommodate this.
From this analysis, some things immediately become clear. Adventure must originate externally. You cannot stay in your room all day and have an adventure. Sorry, but no, that is not possible. You can learn, you can relate, you can even self-actualize, but you do not adventure. Of course it is possible for a call to adventure to be incubated here, but it must eventually go further. Activities like creative pursuits (writing, painting) or meditating can be very productive and very expansive, but they are not adventures. They either rely on introspection or upon our previous experiences. So, that's the first thing to be clear about, adventures are from the external world.
Second thing, adventures are not forced upon you. There is always the possibility to refuse the call or to be blind to the possibilities. There are many little things in life that are calls: random topics that come up in conversation, new people that join you at work, something interesting you read about in a magazine. All these things can be seen as rabbit holes of indeterminate depth. You must first be open to recognizing these for what they are - possibilities - even if more often than not, they are not very deep at all.
With this in mind, we can return to the original question: of where adventure is to be found. We have come to the rather unsatisfying answer that it can be found anywhere. More precisely - it manifests itself any time that some stimulus leads you out of the quotidien and into something new. This doesn't have to involve any travel at all; the sport of parkour is a nice example of how a existing cityscape can be morphed and remoulded to serve a new perspective.
So then why the association of travel with adventure? Well, travel may bring us to the unfamiliar and to the unknown. Travellers have open minds and are searching for something new. At the very least, travel removes us from the everyday. But in itself it may not be sufficient to move us to a different mental plane; we understand now that adventure is something a little more elusive. Best is to follow your existing interests, bring yourself into contact with open-minded people, and keep your eyes open to the call.