This 70-mile stretch of U.S. 550 is a two-lane road, often without guardrails, that slithers up the Uncompahgre Canyon to Red Mountain Pass, plunges down into Silverton, and then climbs Molas Pass for the long descent to Durango. At many points this hair-raising highway follows the original toll road, a cliff-hanging wonder opened in 1883. The modern, paved highway allegedly (1) cost $1 million to build, (2) was constructed on a roadbed made of rich mine tailings, or (3) caused travelers to swear they would not take the road again, even for a million dollars. Another million may have been spent trying to control the Riverside Slide, the most murderous avalanche in Colorado. The Riverside Avalanche Chute (1985) is a concrete highway tunnel overpass for snow slides, which here have killed at least five people and demolished a rotary snowplow.