Alto de la Hundida

Overview

Alto de la Hundida is an endurance test disguised as a moderate gradient. At 39.4 km long it is one of the longest climbs you can point a bike at, and its hors-catégorie rating comes not from savage steepness but from sheer scale. Starting at 635 m and topping out at 2501 m, it delivers 1866 m of net elevation gain, with a total ascent of 2031 m once the small dips and rolls along the way are counted. The average gradient of 4.74% sounds gentle on paper, but sustaining any effort for the better part of two hours reshapes what "gentle" means.

How the Gradient Unfolds

The headline number to respect is the gap between average and maximum. A 4.74% mean laid over 39.4 km means long stretches sit comfortably below that figure, but the 10.38% maximum tells you the road is not uniform. Expect the gradient to breathe: shallow drags where you can hold rhythm, punctuated by steeper ramps that briefly double the effort. The difference between the 2031 m total ascent and the 1866 m net gain — 165 m — confirms there are false flats and short descents woven in, meaning you will climb, level off, and climb again rather than grind a single unbroken wall. Those recovery windows are the climb's one act of mercy.

Pacing Notes

On a climb this long, pacing discipline matters more than raw power. Anchor your effort to your FTP and aim to ride the shallow sections a touch below threshold, saving headroom for the ramps toward the 10.38% maximum. Going into the red early on a 39.4 km climb is unforgiving — there is no short summit to bail you out. If you do not know your threshold, run the numbers through the FTP estimator before you commit, then treat the steeper pitches as the only place you spend above it. With 1866 m of vertical to absorb, steady is fast.

Gearing

Gear for the duration, not just the maximum pitch. The 10.38% ramps are manageable in isolation, but hitting them after 30-plus kilometers of accumulated fatigue is a different problem. A compact 34-tooth chainring paired with a wide-range cassette is the sensible baseline: a 34×32 will get most riders over the steep sections with cadence intact, while a 34×34 buys extra insurance for tired legs on the upper slopes near 2501 m, where thinner air compounds the effort. If you tend to grind, size up to the 34×34 — spinning a lower gear over 39.4 km costs far less than muscling a bigger one.

Summary

Alto de la Hundida rewards patience. Its 4.74% average makes it approachable, but 39.4 km and 1866 m of climbing to a 2501 m summit make it a genuine HC objective. Pace it steady, gear it low, and respect the 10.38% ramps late, and the length becomes an ally rather than an enemy.

Length: 39.4 km
Average gradient: 4.74%
Max gradient: 10.38%
Start: 635 m
Summit: 2501 m
Net gain: 1866 m
Total ascent: 2031 m
Category: HC