The Passo di San Boldo, between Treviso and Belluno, is one of the most spectacular passes in the Veneto: its five spiralling galleries carved into the cliff, built in just one hundred days by the Austro-Hungarian army in 1918, earned it the nickname “staircase to the Dolomites.”
Five spiralling galleries, a First World War engineering feat
From Tovena, on the Treviso side, the road climbs about 5.9 km for 451 m of elevation gain, averaging 7.7% - a figure that hides a far more progressive reality: the first kilometres wind gently along the valley floor before running straight into a seemingly impassable rock wall. That’s where the road plunges into five stacked galleries, blasted with dynamite to supply the Piave front, where the closing hairpins stack up inside the rock itself, some ramps touching 15 to 17%.
Getting the ride right
The difficulty is almost entirely concentrated in the final kilometre, inside the galleries: it pays to save something for this closing ramp rather than burning matches on the gentler opening section. Since the tunnels are narrow and shared with cars on an alternating system, front and rear lights are strongly advised, even in broad daylight, to stay visible in the gloom.
When to go
Almost year-round: this modest climb, topping out at just 706 m, stays rideable from early spring well into autumn. The Giro d’Italia included it on its route in 2019, on a stage linking Treviso to San Martino di Castrozza.
Good to know
Tovena and Trichiana, the villages bookending the pass on either side, offer limited accommodation but make it easy to base a trip around Belluno and the Venetian Prealps, right at the junction between the Treviso plain and the first Dolomite foothills.