The Passo del Mortirolo, between Mazzo di Valtellina and the Passo di Foppa, tops out at just 1,852 m but regularly ranks among the hardest road climbs in the world: 12.4 km at a 10.5% average, without a metre of respite.
A gradient that never lets up
From Mazzo di Valtellina, the road plunges almost immediately into the forest on a gradient that exceeds 12% within the first few hundred metres and locally reaches 18% on the steepest stretches. Unlike longer climbs where the percentages vary, the Mortirolo holds a near-constant difficulty across the entire ascent.
At hairpin 11, a bust in the likeness of Marco Pantani honours the Italian climber who built part of his legend on these slopes during the Giro d’Italia — a customary stop for cyclists making the pilgrimage.
Getting the ride right
A wide-range cassette (11-32 or more) isn’t a luxury on this climb: the relentless gradient rules out any recovery and calls for careful pacing right from the bottom. Best to start well below the effort you think you can sustain.
When to go
June to September, with the road staying rideable without risk of snow over this period. The forest shade over much of the route makes the climb bearable even in peak summer heat, unlike more exposed climbs.
Good to know
Mazzo di Valtellina and Grosio, small Valtellina towns, offer limited but sufficient accommodation for a stopover, with convenient access to the Passo di Gavia, under an hour away by road, for a trip centred on Lombardy’s toughest climbs.