While not particularly challenging in a technical sense, the National Trail is one bad mutha if tackled from beginning to end ? and back. The round trip is approximately 20 miles, the equivalent of walking from 48th Street to 51st Avenue and then turning around and doing it in reverse. The best approach is from the east end, at the Pima Canyon trailhead off 48th Street in Ahwatukee. From there, the National gains about 500 feet in elevation, placing you on the main line atop the mountain. On your journey, you'll pass some of the trail's major landmarks ? The Tunnel, Fat Man's Pass ? before hitting another ascent, this one a moderately difficult 500- to 750-footer that takes you to the very top of the range near the Antenna Array. After you stop to catch your breath, head toward the Rock Shelter on the next peak over. Once there, it's clear ? and mostly level ? sailing along the South Mountain spine, a section of the trail that offers dazzling Valley panoramas amid a pristine Sonoran Desert landscape. The National's west-end terminus is at the San Juan Lookout, which offers an up-close-and-personal view of the snaggletoothed Estrella Mountains.