Fort de Tancrémont, Military fortification in Theux, Belgium.

Fort de Tancrémont is a Belgian fortification on a ridge between Pepinster and Theux, about 18 km southeast of Liège. Only the tops of its five combat blocks show above ground; the rest, including turrets for twin 75 mm guns and three 81 mm mortars, is sunk into the ground. Nearly 2,000 m of galleries lie 20–28 m below the surface.

Built from the 1930s and completed on 8 August 1938, Tancrémont was the last of the four new forts of the Fortified Position of Liège I. Attacked on 12 May 1940, it refused to surrender on 22 May after Battice complied, and held out until 29 May, the day after the Belgian capitulation, when Captain Abel Devos obtained written confirmation of the general surrender order.

The fort is run by the Amicale du Fort de Tancrémont, which descends from the Fraternelle du Fort de Pepinster founded by Captain Abel Devos in September 1942 to reunite the garrison with their families. Visitors tour the site with these volunteers, and the sign at the entrance announces guided visits on Sundays from May to October, 1 p.m. to 5 p.m.

Bring warm and waterproof clothing since underground areas stay cold and damp year-round. A flashlight helps you navigate the dark tunnel sections comfortably.

The underground section extends roughly 30 meters deep into the slate and includes fully equipped rooms such as a hospital and sleeping quarters. These subterranean facilities show how soldiers could live and work below ground for extended periods.