Why would you want to isolate yourself in the clammy confines of your gym when the lovely hills of this city offer an amazing workout opportunity? Sure, you can gauge how many calories per nanosecond you're burning on that running machine, but the ascent up Fillmore Street from Union to Broadway is a far more picturesque way to get the same physiological benefits. You'll start out with long strides until you hit those tricky little steps at Green Street. Pick up the pace and try for every other step, a feat requiring precise coordination. Once you get the rhythm, glance around in awe at the magnificent Pacific Heights homes eternally out of your price range. This should pump your adrenaline even more. Turn around and finish the climb running backward, taking in the glorious views of the bay, the Golden Gate, and the pillowy hills of Marin. Take a quick breather at the top and descend as fast as you can. Because you don't really belong in this neighborhood, now do you?