WRIAD: White Rim In A Day. The 100+ mile loop in the Canyonlands Natl Park that most sane cyclists do with SAG over a few days. Other not so sane riders do it in one shot, pre-dawn to dusk.
The route is not terribly difficult from what I have read. The elevation gain is moderate at, IIRC, 5K' or so. And it is not really all that technical. But 102 miles offroad is still 102 miles and 9 to 12 hours in the saddle is not something to take too lightly. It is remote with no water or supplies over the course and no cell phone coverage. The weather can play into the time it takes to complete the loop and when you are so far in, keeping going is just as good as turning back. Mechanicals need to be dealt with. No easy way to get out of there.
Just one man, all alone, who has a long ways to pedal.
I am intrigued.