Yesterday I went for my first walk of the season in Mount Washington Cemetery. I do this as often as I can. I have a route that is roughly 3.8 miles and takes me about an hour. It's not for the inexperienced! There are altitude changes of several hundred feet; long, slow climbs and steep decents, and vice versa. Good, and good for you, though.
It's not quite as beautiful now as it will be later in the Spring, so start walking now and you'll be ready when it is!