Alto del Aire - Las Lagunas - Las Puertas - Nariño

Overview

Alto del Aire - Las Lagunas - Las Puertas is a hors catégorie climb, the hardest classification there is, and its numbers explain why. Over 23.7 km the road lifts you from a start elevation of 1290 m to a summit at 2908 m. That is 1618 m of net gain, with 1604 m of total ascent — the two figures sitting so close together tells you this is an honest climb: it goes up, and it keeps going up, with almost nothing given back. The average gradient of 6.83% would be demanding over a short haul; sustained across nearly a full marathon's distance, it becomes a genuine test of endurance rather than a sprint of the legs.

How the Gradient Unfolds

The defining feature here is length paired with consistency. A 6.83% average holds steady enough that there are few flat recoveries to break the rhythm, and the max gradient of 12.24% is nearly double the average — a signal that the road stiffens sharply in places. Those steeper ramps are where the climb bites hardest, and at altitudes climbing toward 2908 m, the thinning air compounds every extra percent. Expect the first kilometres to feel manageable, then a slow accumulation of fatigue as the elevation ticks upward. The gap between the 12.24% pitches and the 6.83% average means pacing discipline matters more than raw power.

Pacing Notes

On a climb this long, the single biggest mistake is starting too hard. Anchor your effort to your FTP and hold a sustainable percentage of it for the full 23.7 km rather than chasing the early kilometres. If you don't have a reliable number, run the FTP estimator before you commit to a target. Because the average is 6.83% but ramps hit 12.24%, plan to soften your effort slightly on the shallower sections so you have headroom for the steep pitches — surging on a 12.24% wall near the top of a 1618 m ascent is how riders blow up. Ride the average, not the spikes.

Gearing

For 23.7 km at 6.83% with pitches to 12.24%, gear generously — spinning a high cadence protects your legs across the long haul far better than grinding a big gear. A compact chainring paired with a wide-range cassette is the sensible baseline: a 34×32 will get most fit riders up the steady sections, but given the 12.24% ramps and the sustained 1604 m of climbing, a 34×34 gives you the extra margin to keep turning the pedals when the road kicks and altitude saps your output. If your bike accepts it, err toward the easier ratio — you will not regret the spare gear on a climb this long.

Summary

Alto del Aire - Las Lagunas - Las Puertas is a full-length HC effort: honest, relentless, and unforgiving of a poor pace. Ride it on your FTP, gear low, and respect the 12.24% ramps, and the 2908 m summit is a reward worth earning.

Length: 23.7 km
Average gradient: 6.83%
Max gradient: 12.24%
Start: 1290 m
Summit: 2908 m
Net gain: 1618 m
Total ascent: 1604 m
Category: HC