The Fenestrelle Fortress, better known as the Fenestrelle Fort is a fortress overlooking Fenestrelle (Piedmont, northern Italy). It is the biggest alpine fortification in Europe, having a surface area of 1,300,000 m². The fortress, built by Savoy between 1728 and 1850 under the design of the architect Ignazio Bertola, guards the access to Turin via the Chisone valley and stands at altitudes between 1,100 and 1,800 m. The territory was acquired in 1709 by the Duchy of Savoy (later known as the Kingdom of Sardinia) after the defeat of the French at fort Mutin (Fenestrelle).
The history of modern fortifications in the Fenestrelle area, began in 1690, when the King of France Louis XIV appointed Nicolas Catinat as commander of the French Army against the Duke of Savoy’s Army during the Nine Years' War. General Catinat, better known in Piedmont for his victory at the Battle of Staffarda, the destruction of the Castle of Avigliana and the fire at the Castle of Rivoli, understood the danger posed by the Chisone Valley (Val Chisone) for the French Army and decided to build 3 small redoubts and a fort in the Fenestrelle area. More specifically, in 1694 Nicolas Catinat obtained the approval of Louis XIV to build Fort Mutin. During the War of the Spanish Succession, this imposing fortification was besieged in August 1708 by Victor Amadeus II’s troops and conquered in 15 days.