Galleria dei Saraceni is an old military tunnel from WWI

Galleria dei Saraceni is a high mountain tunnel at an elevation of 2.224m (7,296ft) above the sea level, located in the southwestern part of the Alps, in the Piedmont region, in Italy. The tunnel is currently closed (since 2013). Anyway, there are several works going on to open it again asap. 

The tunnel is also known as Galleria Monte Seguret. The route demands 100% concentration. The road traversing the tunnel is called Strada militare Fenil-Pramand-Föens-Jafferau, Strada militare 79 or Via dei Saraceni. It’s gravel, steep, narrow and dangerous. You can even walk through a motorbike, but before you enter the tunnel, a large pile of clay is loaded to make the passage impossible. There is also a ban and a barrier there.
The road is an old military road from WWI. It has humbled many egos. It’s not for the sissies and shouldn’t be attempted by novice drivers. It’s open from May to October. Take a tip from the tortoise: slow and steady wins the race. The tunnel is located between km 13 and 15. It’s 3 meters wide only. Impassable for 2 cars at the same time.

The construction of the tunnel started in 1925. It finished 4 years later. It still remains an adrenaline-pumping journey and is definitely not for the faint of lungs, heart, or legs. It’s a long - unlit, dark, muddy tunnel. It’s 876 meters long, U-shaped, completely darkened and with deep holes filled with water. To go along is absolutely necessary to carry a powerful flashlight. As makes a turn in the mountains, the first part is completely dark, you hear only the sound of dripping water, is very impressive! The tunnel is unpaved and leaks more than you would see in a normal road tunnel as it is not lined. This leak leads to a stream of water in the tunnel that is often a few inches deep. The end never seems to appear.
Pic: By Gigillo83 (Own work) [CC BY-SA 3.0 (https://creativecommons.org/licenses/by-sa/3.0) or GFDL (http://www.gnu.org/copyleft/fdl.html)], via Wikimedia Commons