Alto de Las Nieves

Overview

Alto de Las Nieves is a climb that refuses to give anything away. Over 22.3 km it averages 9.21%, a number that would be brutal on a five-kilometre wall and becomes almost unthinkable when sustained for this long. You start at 1661 m and finish at 3718 m, a net gain of 2057 m earned through a total ascent of 2109 m — the difference telling you that the road barely relents long enough to lose the extra 52 m along the way. Rated HC, hors catégorie, it sits at the very top of the difficulty scale, above category 1, and it feels every bit of that ranking.

How the Gradient Unfolds

A 9.21% average across 22.3 km leaves almost nowhere to breathe. There are no meaningful descents here — with only 52 m separating net gain from total ascent, the road climbs, and climbs, and climbs again. The defining moment is the 25.04% maximum, a pitch so steep it forces you out of any rhythm you've managed to build. Expect the gradient to swing well above and below the average, but the crucial point is that even the "easy" sections stay hard. At altitude, above 3718 m at the summit, the thinning air compounds every percentage point, so the second half will feel steeper than the numbers alone suggest.

Pacing Notes

The single biggest mistake on Alto de Las Nieves is starting too hard. With 22.3 km at 9.21% ahead of you, discipline in the opening kilometres decides everything. Anchor your effort to your FTP and hold well within it early — the 2057 m of climbing will punish any early surge long before the summit. If you don't know your threshold, get a baseline first with the FTP estimator, then set a target power you can defend for well over an hour. When you hit the 25.04% ramp, accept that power will spike briefly; recover in the pitches that follow rather than trying to hold a steady number through it. Above 3000 m, expect your sustainable output to sag as oxygen thins, so bank nothing on a strong finish.

Gearing

This is a climb that rewards easy gearing and punishes optimism. For most riders, a compact 34-tooth chainring paired with a wide cassette is the minimum. A 34×32 will get many climbers up the sustained 9.21% stretches, but the 25.04% maximum is where that ratio runs out — on a grade that steep, cadence collapses and the effort turns anaerobic. If you have any doubt about your climbing legs, fit a 34×34 or go wider still. Over 22.3 km, the lower gear isn't a luxury; it's what keeps your cadence high enough to survive to 3718 m.

Summary

Alto de Las Nieves is a genuine HC monster: relentlessly steep, punishingly long, and topping out in thin mountain air. Pace it conservatively, gear it generously, and respect the 25.04% ramp, and the 2057 m of vertical becomes an achievement rather than an ordeal.

Length: 22.3 km
Average gradient: 9.21%
Max gradient: 25.04%
Start: 1661 m
Summit: 3718 m
Net gain: 2057 m
Total ascent: 2109 m
Category: HC