I guess it depends on your definition of fun...
Racers are prepping for this weekend's 100-mile Western States Endurance Run, which begins at Squaw Valley, Calif. (6,200 feet) , and climbs 2,550 vertical feet in the first 4.5 miles up Emigrant Pass (8,750 feet).
From there runners follow trails used by the gold and silver miners of the 1850s and climb another 15,540 feet and descend 22,970 feet before reaching Auburn, Calif.
The race starts at 5 a.m. Saturday and runners have till 11 a.m. Sunday to officially finish.
Check out race the Web site to learn more about the event, follow this year's race, do a GoogleEarth flyover of the course, or volunteer to help or run next year. Lots of runners look for pacers, which might be a good way to get a feel for the race before running it.