Forte di Fenestrelle

The Forte di Fenestrelle, perched in Piedmont's Chisone Valley about 80 km west of Turin, is the largest fortress complex in Europe — second only to the Great Wall of China in sheer volume of masonry. Construction began in 1728 under the House of Savoy, resulting in three interconnected forts — San Carlo, Tre Denti, and Delle Valli — linked by a tunnel housing the longest covered staircase in Europe: nearly 4,000 steps climbing 3 km up the mountainside. In the 19th century the fort served as a state prison, allegedly incarcerating political prisoners of the Risorgimento movement, a chapter still debated by historians. Designated an Italian national monument, it is open to guided tours that wind through its casemates, bastions, and the dramatic staircase tunnel, with sweeping views of the surrounding Alpine peaks along the way.