Alto del Infierno

Overview

Alto del Infierno earns its hors catégorie rating the hard way. Over 11.1 km it climbs from 221 m to a summit at 1337 m, a net gain of 1116 m at an average gradient of 10.08%. That average alone tells you plenty: a full-length climb that holds double digits from bottom to top is rare, and it leaves almost nowhere to recover. The total ascent of 1085 m confirms this is a near-continuous drag upward rather than a rolling profile padded with false flats. Add a maximum pitch of 33.16% and you have a climb that punishes both the legs and the ego.

How the Gradient Unfolds

The defining feature here is consistency of pain. With an average of 10.08% sustained across the entire 11.1 km, there is no long shallow run-in to warm into and no plateau to soft-pedal. Expect the road to sit around or above ten percent for long stretches, meaning your effort barely changes from kilometre to kilometre.

The 33.16% max gradient is the headline hazard. A ramp that steep is more than three times the average, so it arrives as a violent spike against an already brutal backdrop. On a pitch like that, momentum evaporates instantly and traction becomes a real concern when you rise out of the saddle. The gap between the 1085 m of total ascent and the 1116 m of net gain is small, which tells you there is virtually no descending mixed in. Every metre you climb, you keep.

Pacing Notes

On a climb this uniform, discipline beats bravado. Because the gradient never relents, going out too hard in the first few kilometres will cost you dearly by the summit. Anchor your effort to your FTP and treat the whole 11.1 km as a single sustained tempo-to-threshold effort rather than a series of surges.

If you do not know your current threshold, run the numbers through the FTP estimator before you commit to a target. Then hold something you can genuinely repeat, because the 33.16% max ramp will force a brief, unavoidable spike above that number. Save a little in reserve specifically for that moment so it does not blow your pacing apart. Elsewhere, keep your cadence smooth and your breathing controlled, and let the steady 10.08% do its slow work without letting your power drift into the red.

Gearing

Gear for survival, not for showing off. At a 10.08% average sustained over 11.1 km, most riders will want the easiest ratio they can fit. A compact 34-tooth chainring paired with a 34×32 is the sensible floor here, and on the 33.16% ramp even strong climbers will be grateful for a 34×34. If your frame and derailleur allow anything larger than a 32 cassette, use it — spinning a light gear protects your knees and keeps you turning through the steepest pitches instead of grinding to a halt.

Summary

Alto del Infierno is a pure, unbroken HC test: long, relentlessly steep, and topped with a savage ramp. Come with low gearing, patient pacing, and respect for every one of its 11.1 km.

Length: 11.1 km
Average gradient: 10.08%
Max gradient: 33.16%
Start: 221 m
Summit: 1337 m
Net gain: 1116 m
Total ascent: 1085 m
Category: HC