There's a nice book-review in the Washington Post of a new book called The Lost Art of Walking. Walking is nature's antidote to depression, and if you're not depressed then it's one of the greatest ways to meditate to pure relaxation. There's a story, I don't know if it's in the book or not, of a man who decided to commit suicide, but he didn't want to do it near home. He walked out several miles into the desert in Southern California, and when he got to his final destination, he felt so good and balanced from the walk, he decided not to go through with it. When I'm in the groove, I usually walk about 5 miles a day, but my record is about 12 miles in a day.
If I remember correctly, it was Nietzsche who said that all great thoughts are conceived while walking. The list of writers who were great walkers is a long one, with Thoreau maybe the most famous.....