Perhaps the most spectacular and frightening 25 miles I have ever driven in my life is Highway 550 between Ouray and Silverton, Colorado. The mountains in this region are giant and literally vertical (unlike the mountains near Denver and Vail that are much more spread out). My brother said Ouray reminded him of the Alps in Switzerland. Ouray is rich in history and architecture with lots of historic mining buildings, hotels, and shops.
At the top is an old mining camp at Red Mountain Pass. Another spectacular spot for photos.
So, the first time I drove Hwy 550, it was raining on the bottom and lightly snowing on the top of the pass. By the time I turned around to drive back, however, it had started to get dark, with blinding snow and fog, and very slick hairpin turns. Even though I had 4WD, I drove about 10mph the whole way home....scared to death!