The steepest 2 kilometers of the top cycling climbs in Colorado. From this page you may navigate to the top 10 steepest bicycling climbs in CO. Colorado's steepest bike climbs we have documented are featured in the slideshow below. Scroll down to access Colorado's steepest 2 km Top 10 Bicycle Climbs "Table". The cycling climbs covering the steepest 2 kilometer gradients in CO, and some of Colorado's hardest and most scenic cycling climbs are, in order of steepness, 1. East Portal, 2. Flagstaff Rd, 3. Magnolia Road, 4. Sugarloaf Rd , 5. Pikes Peak, 6. Rist Canyon West, 7. Trail Ridge, 8. Left Hand Canyon, 9. Slumgulion Pass, and 10. Bellyache Ridge.