The Secret Military Fortresses Hidden in the Swiss Alps


Chloe Berge
Fri, December 10, 2021

Courtesy of Sasso San Gottardo

Unlike most train rides in Switzerland, there is no postcard view of the snow-dusted Alps on the Metro del Sasso. Cold, damp air cuts through the underground funicular as it chugs uphill in near darkness, deep in the Gotthard mountains in the country’s southernmost canton of Ticino. Disembarking at the top, instead of a sweeping bucolic landscape, passengers arrive at a military command center.

Only declassified in 2001, Sasso da Pigna was one in a chain of secret fortresses constructed in the Swiss Alps during World War II. After France fell to the Axis powers in 1940, Switzerland lost a powerful ally, and army general Henri Guisan knew trying to continue to defend the country’s borders against indomitable Germany was futile. Instead, the Swiss National Redoubt was born. The military strategy drew troops away from the front lines, concentrating manpower in impenetrable mountain bunkers.

Fortresses like Sasso da Pigna, built in 1941–45, and two other key citadels at Saint-Maurice and Sargans served as strongholds in a network that stretched across the Alps. They housed troops and artillery, while others acted as hangars for fighter planes. Sasso da Pigna’s location at the Gotthard Pass was a particularly important one. The pass marks the main route through the mountains from north to south and has served as a major trade route through the Alps since the Middle Ages, modernized in the late 19th century with the creation of the Gotthard railway line.


When the fortress was finally declassified, its transformation began into Sasso San Gottardo, a museum that pays tribute to the area’s storied past. “This is where Switzerland started, at the foot of this pass,” says Sepp Huber, a former mountain infantry commander who now leads tours through the historic fortress. Visitors enter through a towering doorway carved into the rockface, big enough to allow tanks to pass through. Overhead, the red, blue, and yellow flags of Switzerland and the cantons of Ticino and Uri—whose border lies half a mile north of the fortress—snap and flicker in the icy alpine wind.

Inside the tunnels of the historic fortress, Sasso da Pigna
Courtesy of Sasso San Gottardo

The garrison-turned-museum tunnels two miles into the mountain, and on the first floor, visitors are greeted by contemporary exhibitions on the region’s natural history and culture. In a darkened gallery, quartz crystals the size of small trees—for which the area is world renowned—shimmer under a spotlight. Past exhibitions have been dedicated to themes such as the area’s renewable energy projects, and next year, the museum will launch a program focused on the work of Goethe. The 18th-century German poet was enchanted with the Gotthard Pass, making three pilgrimages there and writing extensively on this part of the Alps.

Past these rooms, a ride on the Metro del Sasso brings museum-goers to the historic heart of the military operation. Spartan barracks house wood bunk beds dressed in stiff khaki-colored sheets. The walls of a command center are hung with strategy maps bookended by radio transmitters on shelves, and an artillery room leads out to a newly-built terrace, where there’s a view of serpentine roads skirting green mountains veined with snow.

Today, Sasso San Gottardo is open to the public during its short season from May to October, when the pass isn’t sealed off by glittering ice and numbing winds. But during World War II and through to the end of the Cold War, the National Redoubt’s fortresses were shrouded in mystery.

“I’ve often looked out of train windows and seen a steel door in the cliffside, and thought to myself, there might be airplanes behind that,” says Clive Church, a Swiss history expert and professor emeritus at the University of Kent. Civilians knew of the redoubt, but no one knew exactly what was inside, and neither did Germany or Italy, which was part of the strategy to deter their encroachment. “The fortress only housed 400 men, but the Swiss would tell the Germans 4,000,” says Huber.

Historic army barracks at Sasso da Pigna
Courtesy of Sasso San Gottardo

“The Swiss knew that German and Italian spies were concentrated at the fortress construction sites in the central Alps, so they fed exaggerated information into channels they thought might be informing Germany,” adds museum director Damian Zingg. This strategy was part of the country’s longstanding policy of armed neutrality, which dates back to the Congress of Vienna in 1815. European powers collectively decided that keeping the country neutral would help the entire region remain stable, creating a buffer between France and Austria. “The redoubt was there if they were attacked, but it was also there as a dissuasive,” says Church. “The more you created this mythos of an impenetrable fortress that would have to be fought inch by inch up a very steep incline, the less it was something the Nazis thought they were able to do,” adds Church.

The creation of the redoubt was also a way for the Swiss to reassure other powers that they were not covertly assisting the Axis. “For most Swiss [the redoubt] is a symbol; it’s not just the concrete bunkers and the guns,” says Church. “It’s part of their resistance to Nazism.” The Swiss haven’t actually seen combat since the early 1500s but just how neutral Switzerland actually was during the war is contentious. It’s now known that the redoubt was only part of the defense strategy, and that Switzerland continued to trade with Germany and grant them access to the Gotthard railway.

“Switzerland needed raw materials and building supplies from Germany [to construct the fortresses], which it received in exchange for its exports and arms supplies,” says Jakob Tanner, a professor emeritus in Swiss history at the University of Zurich. According to most Swiss historians, these economic relations were, like the redoubt, aimed at deterring Germany from attacking, proving too much was at stake to invade the country.

Airolo, Passstrasse
The Swiss National Redoubt spanned the Alps, hidden in the rockface.
Andre Meier

Although the methods of warfare used in the redoubt became increasingly obsolete after the war, their symbolic nature kept the fortresses in operation. “Neutrality also had a domestic, internal function,” says Tanner. “While the army left the redoubt immediately after the end of the war, the population remained in the mental redoubt, which led to a boom in ‘spiritual national defense’ and anti-communism,” explains Tanner. To that end, the fortresses were used during the Cold War, although information on exactly how and why they were utilized remains restricted. By the 1990s, political stability in Western Europe and the steep maintenance costs associated with keeping the fortresses operational meant that most of them were declassified and sold to private buyers.

Like Sasso da Pigna, the fortress at Saint-Maurice was also converted into a museum. And less than a mile away from Sasso da Pigna at the top of the Gotthard Pass is an artillery bunker, San Carlo, that has been turned into the hotel La Claustra. Opened in 2004, the cavernous refuge was the work of Swiss architect Jean Odermatt and offers 17 rustic rooms surrounded by a lake and miles of hiking trails.

In 11 former bunkers in Stansstad, the company Gotthard-Pilze grows organic mushrooms, and in the region of Giswil, a military fortress called Pfedli is owned by the Swiss cheesemaker Seiler Kaserei AG. Once used for storing ammunition, spare parts for fighter jets, as well as guided missiles, the company now ripens over 90,000 wheels of raclette cheese in the bunker’s two 100-metre-long tunnels, where humidity levels and a temperature of 52 degrees Fahrenheit make an ideal environment for the ageing process.

While the National Redoubt fortresses live out their reincarnations as museums and food production facilities, the threat of the Axis powers seems an almost unimaginable chapter in Switzerland’s past. But it was very real for the thousands of Swiss men and women that served in World War II who filled the dark, subterranean world of the redoubt with their echoing footfall.

Under Switzerland’s emerald hills and the chorus of cow bells, beneath the fairytale chalets and icing sugar mountain peaks, exists a grittier history worth remembering. Long veiled in secrecy, the stories of the redoubt have worked to reinforce the mythic place of the mountains in the Swiss consciousness. “The mountains are the home of Switzerland, they always offer protection to the country,” says Tanner.