The Zion-Mount Carmel Tunnel is a long, narrow bore through a cliff, a mile and a tenth from end to end, and it was one of the great engineering gambles of its time. Crews working in the late 1920s drilled it by hand and dynamite through solid sandstone, and carved a series of windows in the canyon-side wall to let in light and let out dust. Those openings are still there, glimpses of daylight and drop and sky that flash by as you ride, which is as close as you will come to being inside a cathedral on a motorcycle. The tunnel opened in 1930, and for a long time it was the only way across the plateau.
For riders, the tunnel is a unique experience. It is dark, with a low ceiling, cool air and a distinct smell of damp rock, and your headlight should be on. The bore is narrow, and the park service has long regulated large vehicles: they pay a fee and use the centre of the road, and traffic is stopped in the opposite direction while they pass. Motorcycles do not need an escort, but you may find yourself waiting for a motorhome, and the queue of idling engines in a tunnel is a good argument for patience. Stopping inside is forbidden.
The approach is up the Pine Creek switchbacks from Canyon Junction, six tight bends climbing steadily through gorgeous cream and pink rock. East of the tunnel the road emerges into open slickrock country, a gentle, rolling landscape of white domes and pine, very different from the canyon below. In winter, ice and snow can close the road, and spring and autumn are the pleasantest seasons for riding. Watch for bighorn sheep, which often graze near the road.
The nearest fuel is at Springdale on the west or at Mount Carmel Junction on the east, so fill up beforehand. Hildale and Colorado City are on the other side of the plateau, and Hurricane is the largest town nearby. There is no stopping at the tunnel, no services and no water, so plan your breaks before and after. The east side has a viewpoint and a few pull-outs, and the park charges an entry fee at the gate.