Passo dei Laghi Gemelli

Overview

Passo dei Laghi Gemelli is a hors catégorie (HC) climb — the hardest rating on the scale, above categories 1 through 4. Over 29 km it lifts you from a start elevation of 410 m to a summit of 2131 m, a net elevation gain of 1721 m. The average gradient reads a deceptively civil 5.93%, but the total ascent of 1726 m tells the fuller story: this road rolls, dips, and reloads rather than climbing in one clean line. At 29 km long, it is an endurance effort first and a gradient challenge second, right up until the moment a 35.8% max pitch reminds you otherwise.

How the Gradient Unfolds

The gap between the net gain of 1721 m and the total ascent of 1726 m is small — around 5 m of extra climbing — which means there is very little false flat or descent to recover on. Almost every metre of the 29 km is spent going up. That 5.93% average is the number to internalise: it is sustainable for hours, but it is an average, and an HC climb of this length is never uniform. The headline danger is the 35.8% max gradient, a wall far steeper than the average that can appear where the road ramps hardest. Ride the mellow sections smoothly, and treat any steep pitch as a short, contained problem rather than a reason to blow apart.

Pacing Notes

On a climb this long, pacing is everything. Anchor your effort to your FTP and hold a steady, repeatable power rather than chasing the gradient. Over 1721 m of gain, small surges compound into deep fatigue, so err on the conservative side early — you have 29 km to spend. If you do not know your threshold, run the numbers through the FTP estimator before you plan the day. Aim to arrive at the steepest ramps with headroom, because near a 35.8% pitch there is no soft-pedalling: you either have the gear and the legs, or you are walking. Keep cadence up on the gentler 5.93%-ish stretches and save your matches for where the road bites.

Gearing

For a 29 km HC climb averaging 5.93% with a 35.8% max, gear for the worst pitch, not the average. A compact 34-tooth chainring paired with a wide cassette is the sensible baseline. A 34×32 will get most fit riders up the sustained sections, but for the 35.8% wall — and for surviving 1721 m of accumulated gain — a 34×34 gives you a meaningfully lower bailout. If your bike and derailleur will take it, run the 34×34; the extra range costs you nothing on the flatter grades and buys you a spinning cadence exactly when you need one most.

Summary

Passo dei Laghi Gemelli is a long, relentless HC ascent that rewards patience and punishes ego. Pace to your threshold, gear low, and respect the fact that 29 km at 5.93% still hides a 35.8% sting.

Length: 29 km
Average gradient: 5.93%
Max gradient: 35.8%
Start: 410 m
Summit: 2131 m
Net gain: 1721 m
Total ascent: 1726 m
Category: HC