The San Boldo Pass is a small mountain pass in the Italian Veneto region between the towns Trichiana (329 m) and Tovena in the Cison di Valmarino region (272 m) over a distance of 17 km (11 mi).
Comprising of 706m of elevation spread across 17km - and featuring this very unique mountain feature - the San Boldo Pass is known colloquially as the 'strada di cento giorno', or 'Road of 100 Days'. This title was given after its rapid creation - by the Austro-Hungarian Army - between the months of February and June 1918; where a workforce of 1,400 worked through three shifts around the clock to provide the occupying forces with a critical access road for supplies and munitions.
The key feature of the road is this particular mountain climb; with five separate tunnels cut into the rock making the pass feasible - due to it's military use the road could not exceed a 12% incline.
Today the pass is still a very active road in the area , despite the 30km/h speed limit, and single-lane climbs. That said; cycling up this stunning pass is unlikely to result in speeds anywhere close to this imposed limit; as the average 4% incline across the 17km will certainly take its toll!