Hiking is a radical sport that involves walking in natural environments and also climbing using special materials to reach great and of high altitude distances.
Picture taken from here.
One of the things I've never done was go hiking. People say its dangerous and full of adrenaline. I like radical sports and things that would give me a thrill when doing, so I'd probably like hiking. Secondly, the Grand Canyon is enormous and gorgeous, hiking there would not only involve adrenaline, but great sights.