Hikers in the Hidden Valley Natural Area can choose the sensible route: a leisurely one-hour stroll from a well-worn trailhead, through pretty woods, across tallgrass fields, to a platform overlooking a deep, wooded ravine -- a nice spot for a rest or a picnic. But hikers wanting more of an adventure can turn east before reaching the platform, into a tangle of curving, unmarked paths twisting through deep woods. To reach the trailhead from Kansas City, head east from I-35 on Armour Road. Turn north on Searcy Creek Parkway; after a mile, turn east on Russell Road. Watch for a parking area on the left. The trailhead is across the street at the southeast corner of the field.