Alto del Peñón

Overview

Alto del Peñón is a hors catégorie (HC) climb, the hardest classification on the scale before the numbered categories 1 through 4. It runs 9.2 km and averages a relentless 9.97%, a figure that alone marks it as one of the more brutal sustained ascents a rider can attempt. You start at 408 m and finish at 1324 m, a summit elevation gain of 916 m over its length. There is nowhere to hide here: an average that sits within a whisker of double digits means the climb offers almost no recovery, and the pitch you settle into early is roughly the pitch you carry to the top.

How the Gradient Unfolds

The defining number is that 9.97% average across all 9.2 km. On a climb this steep, the story is not whether it gets hard but how much harder it gets on the worst sections. The maximum gradient reaches 15.94% — well over half again as steep as the average — so expect ramps that force you well out of any comfortable rhythm. Because the average is so high, those maximum pitches are not brief anomalies bracketed by flat recovery; they arrive on top of terrain that is already severe. The gap between the 9.97% average and the 15.94% max is the part of the climb that decides your day. The total ascent of 864 m sits just under the 916 m net gain, which tells you the road climbs almost continuously, with only the faintest dips along the way.

Pacing Notes

On a climb averaging nearly 10% for 9.2 km, pacing is everything. Ride it as a steady effort anchored to your FTP rather than chasing the steepest ramps — going deep into the red on the 15.94% sections early will cost you far more than the seconds you gain. Aim to hold a sustainable power just under threshold on the average pitches, and accept that the max ramps will briefly push you above it; that is unavoidable on gradients this steep. If you are unsure of your threshold number, run the numbers through the FTP estimator before you commit to a target. With 916 m to gain, treat the first two-thirds as investment and keep something in reserve for the upper slopes.

Gearing

Gear for the average, not the summit sign. At a sustained 9.97% with ramps to 15.94%, most riders will want the widest range they can fit. A compact 34-tooth chainring paired with a 32-tooth largest sprocket — 34×32 — is the sensible floor here, and many riders will be grateful for the extra relief of a 34×34 on the steepest pitches. If your legs or your bike allow an even easier bail-out gear, use it: spinning a low gear on a climb this steep protects your effort far better than grinding a ratio that is a touch too tall.

Summary

Alto del Peñón is a genuine HC test — short by grand-tour standards but savagely steep, with an average that never lets up and a maximum that punishes any rider who paces it wrong. Respect the 9.97%, gear low, and ride to your threshold.

Length: 9.2 km
Average gradient: 9.97%
Max gradient: 15.94%
Start: 408 m
Summit: 1324 m
Net gain: 916 m
Total ascent: 864 m
Category: HC