This classic loop takes you to the highest singletrack in Washington. You spend a lot of time pedaling at 7000 feet and get as high as 8000 feet. The loop here includes Cooney Lake and Horsehead Pass.
Overview from the USFS: Sawtooth Backcountry mulit-use brochure (pdf).
This is a demanding ride with over 5000' of climbing and descent at elevation, lots of loose rocky conditions and hike-a-bike. Average ride times are 5-8hrs. Please carry plenty of food and water, and budget plenty of time to complete the ride safely. The scenery at Cooney lake is especially gorgeous, but do not spend too long here as it's early on in the ride.