The bunker complex is linked by over 5 kilometers of underground tunnels.
The facility is equipped with a functional narrow-gauge railway originally used to transport ammunition and supplies.
The structure includes an autonomous power plant with massive diesel generators that are still intact.
The underground complex features a fully preserved infirmary and surgical theater from the 1930s.
During the 1940 campaign, the fort successfully fired upon German positions, contributing to the defense of the sector.
The ventilation and filtration system, intended to protect against gas attacks, remains physically present in the gallery system.
Four-à-Chaux was never captured by enemy forces during the 1940 fighting.
The crew assigned to this fort numbered approximately 580 men.
Ouvrage Four-à-Chaux is a preserved fortification of the Maginot Line situated near the village of Lembach in the Northern Vosges. It consists of six combat blocks connected by a network of underground galleries located 30 meters beneath the surface. The site features original armament, including retractable turrets and machine-gun casemates, that remain in their 1940 configuration. Visitors travel through the barracks, hospital, and kitchen areas via a small-gauge electric train used during its active military service. It was one of the largest artillery fortifications in the sector, designed to defend the northern flank against German advances. The site serves as a museum managed by the Association des Amis de la Ligne Maginot. Maintenance of the underground mechanical systems allows for historical reenactments and educational tours.
The main entrance block with its imposing concrete facade and steel armored shutters.
Bring a warm jacket, as the underground temperature remains constant at approximately 13°C year-round regardless of outside weather.
Wear sturdy, closed-toe walking shoes to navigate the concrete flooring and narrow tunnel environments.
Book your visit in advance if traveling in a group, as access is restricted to guided tours.
Do not attempt to explore beyond the guided path, as the underground network is complex and hazardous.
Closed on Mondays and Tuesdays during the off-season; check website for seasonal winter closures.
Maintain silence in memorial areas; follow the guide's instructions strictly regarding restricted zones.
