There are a couple strenuous hikes in Joshua Tree, but the ones that have been ranked among the hardest are Warren Peak Trail and Ryan Peak Trail. Both hikes have steep inclines and require the appropriate gear to complete. Warren Peak trail takes about 3-4 hours to complete and will have your leg muscles weak by the time you finish. Other difficult hikes in Joshua Tree include Mastodon Peak, Wall Street Mill Hike, Boy Scout Trail, and Squaw Tank Trail Hike.