Cascade Loop Highway. Where: Washington Length: 440 miles Recommended drive time: Three days Scenery: Mountains! Islands! Rivers! Lakes! Valleys! You name it, the Cascade Loop Scenic Highway has it, taking drivers through numerous distinct regions including the Methow Valley, the Columbia and Snohomish River Valleys, the Cascade-Leavenworth Foothills and Whidbey and Fidalgo Islands.