San Boldo Pass, Italy

San Boldo Pass or Passo San Boldo is a small amazing mountain pass located in the Italian Veneto region between the towns of Trichian and Tovena. The mountain pass was previously known as Passo Sant’Ubaldo and Umbaldopass. The mountain pass lies at the southern edge of the Alps and links the Val Belluna with the Val Mareno over a height of approx. 706 meters. The mountain pass is named the SP 635 (former SS), through the so-called Canale della Scala or San Boldo (in dialect Canal de San Boit) has considerable historical importance, and only one lane is drivable, the traffic is controlled by several sets of lights. There is a speed limit of 30 km/h (19 mph) and a height limit of 3.2 m (10.5 ft.), after buses were frequently stuck in the tunnel. The five tunnels blasted into the rock with hairpin turns or loops, and six bridges.

Italian sheperd Luigino Balzan and his flock are reaching San Boldo pass. The pastor Luigino Balzan leading the flock towards the last curves of the pass san Boldo, between the province of Treviso and that of Belluno. Image credit giancarlo rado Bighugelabs

Although the need to rebuild the steep road over the San Boldo pass into a motor-able road was clear by the end of the 19th century, this project languished until the Austro-Hungarian army accomplished it from February to June 1918 as part of its World War I logistical efforts. The road to supply the Piave front was built in only three months, under the direction of Ing. Giuseppe Carpenè. Due to its short construction period, it is nicknamed the "Road of 100 Days." Prisoners of war, the elderly, women, and children of the local population were pressed into service to build it. In its final construction phase, 1,400 workers worked in three shifts to build this strategically important connection. Despite the extreme topography, the requirement that the road be used for transporting heavy artillery and supplies meant that the grade could not exceed 12%. [Source]