The Crystal Mill Falls river run on the Crystal River in Colorado is a Class III-IV rapids section with several challenging obstacles, including Sledgehammer, Hell's Half Mile, and Meatgrinder. The best time to float this section is in the late spring or early summer when water levels range from 400 to 800 CFS. The run requires intermediate to advanced skills and knowledge of river safety. It is essential to have proper gear, including helmets, PFDs, and drysuits. Overall, the Crystal Mill Falls run is a thrilling adventure for experienced whitewater enthusiasts.