Expensive boot camps and pricey gyms are great for staying in shape. So are skiing, kayaking and cycling — if you can afford all the gear that goes along with those sports. But if you want a real workout — one that tasks even the fittest of the fit — try running, jumping or climbing the 69 rows at Red Rocks Amphitheatre, or the stairs next to them. The place is gorgeous, and free, and you'll find people just as crazy as you, sometimes in large, organized groups, there year-round on just about any day when there isn't a scheduled concert or event. Right now the city allows anyone or any group to use the stairs, as long as they are considerate of others and respect the quiet beauty of the place.