Many years ago, but this used to be one of my favorite things to do when I was a kid. Liked trees better than regular playground equipment. Would play "Tarzan" and swing from branches, and build "tree houses."
I've never climed a tree per say, but the area of WV I live in has trees everywhere. Anyway, this question made me nostalgic, because when I was much younger we had a tree in the yard. It had grown in such an odd manner, and it had a slit in the center where it had divided - not sure how that happened. I would sit on it and look at the stars at night.