Cactus to Clouds is a worthy endeavor. Almost 11,000 feet of climbing in 15 miles making it what many consider the toughest day hike in the country. I did it a few years ago and found it about as challenging as a R3.

It's in Palm Springs on San Jacinto Peak, start behind the art museum and start heading up. A couple of spots to get water along the way. Most people do the hike by hitting the peak and then taking a tram back down. Makes the hike 22 miles. The trail is so steep below the tram going down that almost everyone I know that's attempted to hike back gets into trouble some how. Once at the end of the line for the tram, call a cab and it's a $25 ride back to your car in downtown Palm Springs.