Puerto del Castillo

Overview

Puerto del Castillo is a 9.5 km category 3 climb that lifts you from a valley floor at 537 m to a summit of 892 m. The headline number is friendly: an average gradient of just 3.75%. That places it firmly in the "long tempo effort" bracket rather than the leg-breaking category-1 or hors-catégorie world. But the average tells only half the story. With a maximum pitch of 10.02%, the climb hides steeper ramps inside an otherwise steady profile, so treating the whole thing as a flat 3.75% drag is a mistake that will cost you late on.

The net elevation gain is 355 m, while the total ascent logged is 351 m — a near-perfect match that confirms this is an honest, continuously rising road with almost no false flats or descents to break the rhythm. What you climb, you keep.

How the Gradient Unfolds

The gap between the 3.75% average and the 10.02% maximum is the whole character of this climb. If every metre were at the average, you would never see anything above 4%. Instead, the road banks steepness into a handful of ramps that spike toward double digits, then relaxes into shallower sections that let you recover.

Do the arithmetic on the shape: 355 m of net gain across 9.5 km is what produces that 3.75% mean. Where the road kicks toward 10.02%, roughly two and a half times the average, you are borrowing effort that the flatter stretches will hand back. Read the climb as a series of surges rather than one uniform grind, and you will arrive at 892 m with something in reserve.

Pacing Notes

Because the average is moderate, the temptation is to attack from the bottom. Resist it. On a climb this length, the smartest approach is to hold a steady power just under threshold and let the gradient dictate your speed rather than your cadence.

Anchor your effort to your FTP. A climb of 9.5 km at 3.75% will typically take a fit rider somewhere in the tempo-to-sweetspot range, so aim to sit a touch below threshold on the flatter sections and allow yourself to drift up toward it only on the 10.02% ramps. If you do not know your number, run the FTP estimator first — pacing this climb well depends entirely on knowing where your ceiling sits.

Gearing

For a climb averaging 3.75% you do not need extreme ratios, but the 10.02% maximum is steep enough to punish an over-geared setup. A compact chainset paired with a 34×32 low gear is plenty for most riders to spin the steep ramps without grinding.

If you are carrying fatigue, tackling this at the end of a long day, or simply prefer to keep your cadence high, drop to a 34×34. That extra sprocket costs you nothing on the shallow 3.75% sections and buys real comfort where the road hits double digits. Between 34×32 and 34×34, you have the whole climb covered.

Summary

Puerto del Castillo rewards discipline over aggression: pace the shallow stretches, respect the 10.02% ramps, and let the honest, near-continuous 355 m of gain carry you to the top.

Length: 9.5 km
Average gradient: 3.75%
Max gradient: 10.02%
Start: 537 m
Summit: 892 m
Net gain: 355 m
Total ascent: 351 m
Category: 3