I discovered Black Canyon of the Gunnison National Park on the map when I was researching a trip to ride Colorado. The south rim is 7 miles north on CO Highway 347 off U.S. Highway 50, just east of Montrose, CO.
"Big enough to be overwhelming, still intimate enough to feel the pulse of time, Black Canyon of the Gunnison exposes you to some of the steepest cliffs, oldest rock, and craggiest spires in North America. With two million years to work, the Gunnison River, along with the forces of weathering, has sculpted this vertical wilderness of rock, water, and sky."
A great story by Ken Bingenheimer with photos is on Eagle Rider's forum.