Tough, meet tougher. In our quest for challenges that make our lungs want to explode, this ride presents itself as a badass, uphill-on-gravel test piece. Start at the fancy Gateway Trail, where some uber-fit hikers may actually outrun you on some of the steeper portions. Don't be too impressed. You'll work as hard or harder as a hiker on this one, even using your best granny gear. It's a solid six miles to the base of Tom's Thumb from here, and a grueling slog the whole way. Which is how we like it. Throw in a Sonoran Desert setting that would impress any out-of-towner, and you've got the makings of a killer day, metaphorically speaking. Take lots of water. When done, zoom back down the way you came like a bobsled. For us, it's a crazy memory. But maybe it'll be your new morning routine.