Alto de Letras

Overview

Alto de Letras is one of the longest continuous paved climbs on Earth — a hors catégorie ascent that runs 68.8 km from the Magdalena valley town of Mariquita, at just 464 m, all the way to the 3,658 m pass on the Cordillera Central. Over that distance it gains 3,182 m of net elevation at an average gradient of 4.52%. The numbers look gentle on paper, but nothing about Letras is gentle: you climb for the better part of a working day, and the final third is ridden in thin air above 3,000 m.

How the Gradient Unfolds

The defining feature of Letras is its relentlessness rather than its steepness. The average sits at 4.52% and the steepest sustained ramps reach only about 12%, so there is no single wall to fear — instead the road simply refuses to stop going up. Total ascent over the climb is 3,596 m, barely more than the 3,182 m net gain, which tells you how little respite the profile offers: there are almost no descents to recover on. From Mariquita the grade eases you in through humid low-altitude forest, stiffens through the middle sections around Fresno and Padua, then drags on for tens of kilometres of open páramo toward the summit.

Pacing Notes

On a climb this long, pacing is everything — go out too hard on the warm lower slopes and the altitude will collect the debt with interest up top. Ride it as a sustained tempo effort well below threshold; knowing your FTP turns that from guesswork into a plan. If you don't have a recent number, our FTP estimator will get you close enough to set a wattage ceiling you can hold for four-plus hours. Above 3,000 m your sustainable power will fade, so bank nothing on the early gentle gradient.

Gearing

Because the gradient rarely bites hard, gearing here is about comfort over many hours rather than surviving a single steep pitch. A compact 34-tooth chainring paired with a 32 cassette (34×32) is plenty for most riders across the 4–5% majority of the climb and keeps your cadence spin-friendly enough to protect the legs. If you tire late or want insurance for the thin-air final ramps, a 34×34 keeps something in reserve for the highest, slowest kilometres.

Summary

Alto de Letras is a bucket-list climb defined by sheer scale rather than gradient — a full-day ascent from tropical valley to high páramo.

Alto de Letras — Mariquita side

• Length: 68.8 km
• Average gradient: 4.52%
• Max gradient: 12.31%
• Start: 464 m (Mariquita)
• Summit: 3,658 m
• Net gain: 3,182 m
• Total ascent: 3,596 m
• Category: HC