Moab—the place to bike for all serious riders—joins cracked sandstone trails and slickrock steeps that are challenging even for experts. West of Moab, you can take the 13-mile loop, which climbs over 1,000 feet in elevation onto Poison Spider Mesa. It descends fast and sharp along Portal Trail, your return route. Though it’s not too technical, you’ll plow through deep sand in areas, which can be brutal on your muscles. Bring plenty of water for the harsh, dry desert climate. You won’t find mountain streams to filter H2O here.