Good old US 666 starting in Gallup, New Mexico passing through Colorado before ending at Monticello a short distance across the Utah boarder. The land is barren, but beautiful in a harsh dry way. I love going down there not only because of scenery, but because it is so much fun to say, "I'm going to drive The Devil's Highway."
Interesting places near the route include part of Hovenweep National Monument, Mesa Verde National Park, Yucca House National Monument, and the Four Corners tourist trap. Chaco Canyon is somewhat nearby as well, in New Mexico.
Some of the sights visible from the highway include Abajo Peak, Sleeping Ute Mountain, Hesperus Peak (barely visible, but another killer name! I had to mention it.), Ship Rock, and the Chuska Mountains.
One of my favorite memories was driving from where we were camped near Cortez down highway 666 and then off on US 160 to Four Corners. I was with my dad, sister, and an exchange student from Russia. The truck was too hot and so we cruised with both windows down at 75 miles an hour across the cholla covered flats. Despite the oppressive heat we had great fun joking back and forth, sharing around the water, looking at Ship Rock, and discussing interesting English phrases.