Alto del Diamante

Overview

Alto del Diamante is a long, high-altitude test that rewards patience over aggression. At 25.6 km with an average gradient of 5.2%, it sits firmly in the endurance category rather than the pure-power bracket — this is a climb you settle into rather than attack. It begins at 966 m above sea level and tops out at 2296 m, a summit high enough that the thinning air becomes a factor in its own right by the final kilometres.

The headline numbers tell a story of scale. The net elevation gain is 1330 m, while the total ascent is 1425 m — that 95 m difference means the road is not relentlessly uphill. There are short descents or flat interruptions woven into the ascent, giving your legs brief reprieves but also breaking your rhythm if you let them. And lurking somewhere in that profile is a 20.69% maximum gradient, a wall roughly four times steeper than the average that demands respect no matter how strong you feel.

How the Gradient Unfolds

Do not be lulled by the 5.2% average. On a climb this long, an average is a blend of very different terrain. With a peak pitch of 20.69% against a 5.2% mean, the road clearly swings between gentle drags and brutal ramps. Expect stretches where you can spin comfortably in the saddle, punctuated by pinches that force you out of it.

The 95 m gap between total ascent (1425 m) and net gain (1330 m) confirms the profile is not a clean staircase. Those recovery sections are gifts — but they also mean the climbing portions must be steeper than 5.2% to compensate, so the hard kilometres are harder than the average suggests. Manage the ramps, float the flats, and never spend all your matches on a single wall.

Pacing Notes

Over 25.6 km, discipline is everything. Aim to ride the bulk of the climb just below your FTP, holding an effort you could sustain for well over an hour, and reserve a small buffer for the steep pitches near that 20.69% max. If you don't know your threshold, run the numbers through the FTP estimator before you set your target power or heart-rate ceiling.

Because the summit reaches 2296 m, altitude will quietly erode your ceiling in the last third — power that felt easy at 966 m will feel taxing up high. Start conservatively, expecting to feel stronger relative to the terrain than your legs actually are, and let the effort come to you rather than chasing it early.

Gearing

For a 25.6 km climb with 20.69% ramps, gear low and gear generously. A compact 34-tooth chainring is the sensible front end. Pair it with at least a 34×32 for the sustained middle sections, but given the maximum pitch and the 2296 m altitude sapping your legs, a 34×34 is the smarter choice for most riders — that extra sprocket keeps your cadence alive on the steepest ramps instead of grinding you to a crawl. When in doubt, take the easier gear; spinning up 1330 m of climbing beats muscling it.

Summary

Alto del Diamante is a category 1 endurance climb defined by its length, its altitude, and one genuinely fearsome ramp. Pace it patiently, gear it low, and respect the summit air.

Length: 25.6 km
Average gradient: 5.2%
Max gradient: 20.69%
Start: 966 m
Summit: 2296 m
Net gain: 1330 m
Total ascent: 1425 m
Category: 1