Million Dollar Highway (Colorado)

Twenty-five miles of US 550 between Silverton and Ouray with no guardrails, 10,000-foot passes, and drops that make your palms sweat through your steering wheel. The name might come from the million dollars per mile it cost to build in the 1880s, or from the gold ore in the fill dirt — nobody's sure, and the drive is too terrifying to think about etymology. The route passes through the San Juan Mountains, some of the most dramatic geology in North America. Don't look down. Seriously.