I do not like adventures, mostly because I am a lazy person. However, if I were in this situation, I would probably embark on a Safari in Africa. I would love watching nature and wild animals. Another reason for my choice is that this type of adventure is not tiring: you just sit and watch in a car. Of course, it has some risks because a group of hungry lions could pose some danger but I think that these kind of tours nowadays are usually well-organised.
Writing about a Safari has made me think about similar adventures to a Safari tour. Is there anything else? Perhaps a guided tour to a famous or unique natural location. The focus of such guided tour does not have to be animals; it can be nature itself. I think a tour to the rain forest in South America would be a good idea. That place has unique fauna – visiting it would be great experience, as long as it is safe. Adventure does not necessarily need to correlate with the level of safety. Something can still be safe and adventurous at the same time. I would take a lot of photos and videos but I would definitely observe and study the place.