The Tunnel 1 to Golden Whitewater Park river run in Colorado is a fun and challenging Class III-IV stretch of water. The obstacles on this section include the Entrance Rapid, the Castle Rock Rapid, and Supermax Rapid, which all require precise maneuvering. The best time to float this section is during the late spring and early summer, when water levels range from 700-1,200 CFS. Floaters should be experienced and have proper gear, as the rapids are technical and require good control.