Mt. Wilson challenge

What: A two-day 23-mile loop up to 5,710-foot Mt. Wilson and back.

Rating: Tough. Includes steep paved and dirt climbs, and descents on fire roads. Extreme grades up to 15%.

Route: Day 1: Starting at the Cheney Trail in Altadena, turn onto the steep paved section of the Mt. Lowe Railway, which becomes dirt and levels out after 2.3 miles. Free camping is available at the Mt. Lowe Trail Camp at mile 5. Day 2: Continue 3 miles through the Mueller Tunnel, then take Red Box Road 2.5 miles to Mt. Wilson. Stop for lunch and sightseeing, then descend 8.7 miles and 4,400 feet on the Mount Wilson Toll Road. About 3 miles from the bottom, campsites are available at Henninger Flats. Finish the loop with a 3-mile ride on streets back to your car. Highlights: At Mt. Wilson, stop for lunch at the Cosmo Cafe, historical exhibits and telescope viewing. At Henninger Flats, enjoy the panoramic views of the San Gabriel Valley, a fire lookout tower and a tree nursery operated by the L.A. County Fire Department. Visitor center: (626) 794-0675.