Ouvrage Rohrbach, Military fortification and museum in Bettviller, France.

Ouvrage Rohrbach is an underground military complex in Bettviller featuring multiple infantry blocks, gun casemates, and shelters built into a slope above the Saar valley. The structures extend beneath the surface and link artillery batteries, machine gun positions, and supply areas through an interconnected tunnel network.

Construction of the three infantry blocks began in 1934, after budget cuts reduced a planned ten-block ouvrage to a first-phase work costing 10 million francs. In June 1940 the garrison exchanged fire with German troops, losing Lieutenant Damour on 15 June, and surrendered on 30 June after the armistice. German forces evacuated and sabotaged the ouvrage in December 1944; it was repaired in the early 1950s and deactivated in 1970.

The fort is also called Fort Casso, after Abdon Robert Casso (1912-2002), who began his engineering career in September 1935 working on the Maginot Line, including this ouvrage. Since 1989 the Association Fort Casso has run the site as a museum, and local residents had worked on its restoration since 1987.

Guided tours are the best way to explore the underground tunnels, gun emplacements, and machine gun positions while learning about the military engineering of the fortification. The pathways include uneven ground and confined spaces, so sturdy shoes and careful attention are recommended.

The fort is named Fort Casso after Lieutenant Abdon Robert Casso, who in September 1935 helped design and build Maginot Line works including this one. The Association Fort Casso, founded in 1989, runs it as a museum.