The Avalanche Down River Run on the Crystal River in Colorado is a thrilling Class IV-V run with challenging rapids and obstacles such as drops, boulder gardens, and steep chutes. The best time to tackle this run is in late spring or early summer when water levels are at their highest, with recommended flows between 500-1000 cfs. This is not a run for beginners or intermediate paddlers, as it requires advanced kayaking or rafting skills and experience. The narrow and technical nature of the river demands precise navigation, making it an exhilarating challenge for experienced thrill-seekers.