As anyone who has ridden the California Zephyr in any of its incarnations can testify, the Denver & Rio Grande Western's Dotsero Cutoff is one endless sequence of breathtaking views, one after another, with the Colorado River always in view. A bit of Colorado River Road can be seen in this slide, and it's well worth an afternoon's drive; as of 1996 at least it was quite drivable by an ordinary (non-off-road) motor vehicle, although unpaved hard gravel in places.
