This Scottsdale gym allows us to get high — about 30 feet — all by our lonesome by using mechanical auto-lockers mounted at the top of select climbing walls. It's almost like free-soloing, which is climber-speak for scaling vertical cliffs without a rope for protection, except that nagging risk of imminent death is eliminated.

The gym has plenty of regular roped climbs on which you'll need a belay partner. But with the auto-locker, once you climb to the top of the wall, you just leap into space. As long as you clipped the rope to your harness properly, the machine catches you after a couple of feet, slowing paying out the line until you're back on Earth. We got a serious little thrill the first few times we tried it — kind of reminded us of jumping off the roof into the pool when we were kids and our parents were busy inside the house.

The bouldering area is outstanding, too, with long overhanging sections and soft rectangular pads to place under each problem we're working.

The best part about climbing alone: We never have to worry some crazy climbing buddy will cut our rope, like in Touching the Void.