Alto de La Caja

Overview

Alto de La Caja is a long, sustained Category 1 ascent that asks for patience before it asks for power. Over 18.9 km the road lifts you from 1568 m at the base to a 2743 m summit, a net gain of 1175 m. That is a climb measured in tens of minutes, not seconds — the kind of effort where a steady head matters more than a fast start. The average gradient of 6.21% sounds civil on paper, but averages flatten the story: with a maximum pitch of 12.93%, there are ramps here that roughly double the mean. Add the altitude — you finish above 2700 m, where the air is noticeably thinner — and La Caja becomes a test of both legs and lungs.

How the Gradient Unfolds

The headline number, 6.21% over 18.9 km, describes a climb that never truly relents but also never fully explodes. The recorded total ascent is 1147 m against a net gain of 1175 m, meaning the profile is close to monotonic — you climb almost the entire time, with very little false-flat or descent to break rhythm. The gap between the 6.21% average and the 12.93% maximum tells you where the difficulty hides: in the steeper pinches that sit well above the mean. Expect long stretches near the average punctuated by ramps that force a gear change and a moment of honesty from your legs. Because the summit sits at 2743 m, the final third of the climb is where altitude compounds gradient — the same 6% feels heavier the higher you go.

Pacing Notes

On a climb this long, discipline early is everything. Aim to sit at or just below your threshold for the opening kilometres rather than chasing a number on the steeper ramps. A useful anchor is your FTP: treat it as your ceiling for the day, not your target, and let the steep pitches nudge you above it only briefly before you settle back. With nearly 19 km of climbing, a couple of overcooked minutes early can cost you many minutes late. If you are not sure what threshold to hold, run the numbers through the FTP estimator first, then subtract a little for the thin air near the top.

Gearing

Gear for the maximum, not the average. The 12.93% pitches on a climb finishing above 2700 m will punish anyone under-geared, so err toward an easier setup. A compact 34-tooth chainring paired with a 34×32 cassette is a sensible baseline for most riders here, giving you a bailout gear that keeps your cadence up on the steep ramps. If you carry endurance or altitude-limited legs — or simply want insurance across 18.9 km — a 34×34 is the smarter choice, trading a touch of top-end for the ability to spin rather than grind when the road tilts hardest.

Summary

Alto de La Caja rewards restraint: pace the long middle, save something for the thin-air finish, and gear low enough to keep spinning through the 12.93% pinches. Get those three right and 18.9 km of sustained climbing becomes a rhythm rather than a fight.

Length: 18.9 km
Average gradient: 6.21%
Max gradient: 12.93%
Start: 1568 m
Summit: 2743 m
Net gain: 1175 m
Total ascent: 1147 m
Category: 1