The Fenestrelle Fortress is a historic military complex located in the Piedmont region of northern Italy. Built by the House of Savoy in the 17th and 18th centuries, it was designed to defend against French invasions and served as a strategic stronghold. Stretching across three hills with an impressive system of walls, tunnels, and barracks, it is one of the largest alpine fortresses in Europe and now serves as a museum and tourist attraction.