While most of us go out of our way to not run, there is a select segment of our society that actually seeks out this kind of physical activity. For those strange, strange people, Fountain Valley's Mile Square Park provides a lovely opportunity to work the cardiovascular system and keep good track of your distance. Aptly named, Mile Square Park does, in fact, occupy a square mile of urban green space in Fountain Valley, making your pedometer unnecessary. Run up one side? You've done a mile. Circle the whole park? Okay, sorry: Square the whole park? You've run more than we ever have . . . cumulatively. Not content to merely keep to the perimeter? Mile Square also boasts a running path through its interior, where picturesque lakes, picnickers and nature centers whiz past your face in a blur. But you might have to summon up your sophomore-year geometry skills to figure out how far you've gone. This will be on the test. . . .