Some speakers at the hearing said they resented the pressure to say yes, which they said is bearing down on their small rural communities from local chambers of commerce and politicians, led by Gov. John W. Hickenlooper, a vocal enthusiast.

Others said the project, in seeking to create art in the midst of an already stunning natural setting in a rugged river valley, would diminish nature by presuming to improve upon it — a prospect that would offend true lovers of Colorado’s wild beauty and keep them away.

“Coloradans are not New Yorkers — they come to the mountains for scenery, wildlife, recreation and peace and quiet,” Ellen Bauder, the vice president for science at ROAR, said in remarks to the commission. “Bumper-to-bumper traffic, stoplights in the middle of nowhere and long lines are not their idea of recreation, and no amount of public relations is going to make it so,” she added.

The lawsuit, filed on ROAR’s behalf by a group of students at the University of Denver’s Sturm College of Law, argues that land managers did not adequately address the long-term effects of the project on wildlife, especially the bighorn sheep that clamber about on the canyon’s cliffs.

And in classifying an art project as a “recreation activity,” the suit says, the federal analysts framed their assessment in ways that excused the impact of the thousands of bore-holes, rock-bolts and anchors that will have a cumulative effect, the suit says, not unlike industrial mining.