Colorado is where pavement in North America runs out of continent to climb. Mount Blue Sky tops out above 4,300 m, the highest paved road anywhere on the continent, with Pikes Peak a few metres lower across the valley, and Trail Ridge Road, Independence Pass and Cottonwood Pass all crossing 3,650 m.
These are graded tourist highways rather than goat tracks, which is exactly what makes them rideable: long and steady, with the air itself becoming part of the gradient somewhere above 3,000 metres.