The Fenestrelle Fort consists of three fortified complexes: the San Carlo, the Tre Denti and the Delle Valli, joined by a tunnel inside which runs the longest covered staircase in Europe, with 4,000 steps. It has an area of ​​1,350,000 square meters of compendium and a length of 3 km distributed over 650 m of altitude.

The Fenestrelle Fort made its entrance on the stage of History in the autumn of 1727, when the engineer Ignazio Bertola, at the request of King Vittorio Amedeo II, presented the project of a work that had something fantastic: a great wall, studded with from several fortification works, placed as a barrier of the Chisone valley against foreign invasions.
Its architecture is incredible: it develops on the mountain ridge for a length of over 3 kilometers, with a total area of ​​1,350,000 square meters and a difference in height between the first and the last building of about 600 meters . Looking at it as a whole, we are faced with a work out of any canon, when referring to the previous fortification defense techniques, due to its gigantic dimensions and the articulation of its buildings.
Construction work began in the spring of 1728 under the direction of Bertola himself, assisted by the engineer Varino de la Marche, and lasted for over a century. The last construction site closed in 1850. In the years of greatest operational commitment, the number of workers exceeded four thousand units.
Little by little, what was to become the largest Alpine fortress in Europe was born.
It is a fortified complex made up of eight defensive works, some large such as the San Carlo Fort, and others small such as the Santa Barbara Reduced, but each of them had a specific role in the defense strategies.
All the structures are connected to each other through both internal and external paths, but above all through the well-known "covered staircase", a work that stands out for its uniqueness: 4000 steps, protected by two-meter thick walls, climb the slope of the mountain, like a long tunnel that runs continuously for more than two kilometers.

The fort was always a military garrison and constantly maintained its function as a sentry and defensive bulwark but, as with all fortresses, it also carried out the delicate task of a state prison. The rooms of his palaces were often used as detention cells for prestigious personalities, while the barracks' wards housed the so-called common inmates: people convicted of various crimes, soldiers guilty of serious transgressions and, not to forget, a thousand soldiers of the conquered the Kingdom of the Two Sicilies who remained there about a month before being included in the nascent Italian Army.
After the Second World War the fort suffered a total abandonment. The vegetation began to invade and unhinge the walls, so much so that the whole complex risked turning into a ruin, a victim of time and human neglect.
Today, thanks to the San Carlo Project Association, the Fenestrelle Fort is a monumental complex that has been open to the public for some years and has become a place of interest for tourists and scholars who want to savor the charm and mysteries of history through its walls.

There are three possibilities for guided tours: The "Royal Walk" (7 hours), the "Fascinating journey inside the walls" (3 hours), the "Short visit" (about 1 hour).