This 44-mile route links Boulder and Escalante and winds its way up and down mountains and past the Box/Death Hollow Wilderness Area. Mainly gravel and offering unforgettable views into canyons far below, it's slow drive but well worth taking if you have the time. The highlight of the drive is Hell's Backbone Bridge; while the original wooden structure has now been replaced by a modern concrete bridge, the 1500 ft drop-offs to either side are still not for the faint-hearted!
If you go:
If your itinerary permits, try to drive the more direct Scenic Byway 12 route between Escalante and Boulder too; both routes are among the most spectacular anywhere in the US.
Links:

Hell's Backbone Road
Boulder, Utah 84716 USA
Mailing address:
Scenic Byway 12 Foundation
P.O. Box 132
Tropic, UT 84776 USA
Message from RoadTrip America