Legendary Climbs: Mortirolo
Statistics - Passo del Mortirolo from Mazzo di Valtellina, Italy
Length - 12,2km / 7,6 miles
Elevation Gain - 1326m / 4350ft
Average Gradient - 10,8%
The Mortirolo is a giant in World Cycling. It is not the longest or the highest climb, but it is one of the steepest. The climb averages 10,8% with multiple 100m sections averaging ~18%. The Mortirolo is renowned to be one of the hardest climbs in World Cycling, and without a doubt it lives up to its expectation.
I first rode the Mortirolo in the Fall of 2025 on a big Mountain ride passing through the Engadin Valley in Switzerland, over Livigno, and into Italy's Lombardy Region. After already ~3000m / 9850ft of climbing in the legs, we reached the town of Mazzo di Valtellina. (There are 3 different roads to the Summit of Mortirolo, but the most famous side is from Mazzo di Valtellina.)
The Mortirolo starts on a cobblestone street in Mazzo di Valtellina and narrows into a road that leads all the way to the Summit. Once the road narrows, the gradient also kicks-up to double figures all the way to the top. In the first 2km, I found myself already struggling to spin my 37 x 33 gearing. There is no way around the gradient on the Mortirolo, it is a grind to the Summit no matter what gearing you have. On the Mortirolo, the sections below 10% also strangely feel like a recovery, so be sure to spin the legs in these sections and prepare for the next ramp. This is one steep climb! (I remember the road being so steep that my front wheel would regularly lift-up from the tarmac.)
