Mitchell Canyon Staging Area, Mt Diablo State Park, Clayton, CA. Promises to push even the most seasoned trail runner to the max. The nearly 13-mile Vertical Challenge course is indeed devilish, driving you up and over 5 incrementally higher peaks in the first 7 miles before rewarding you with heavenly views from Mount Diablo’s summit, where geologists claim you can see more of earth’s surface than anywhere outside of Mt. Kilimanjaro.