In 1898 a neighboring railway was built from Liège to Barchon. It then climbed from Barchon to Blegny, Trembleur and Dalhem where the tunnel saw the light of day in 1904. The route continued via Mortroux and Neufchâteau to 's-Gravenvelden. The first train that drove to Voeren via the tunnel was a freight train from the Trembleur coal mine. In 1907 the first passenger train reached Dalhem and just under a year later, in March 1908, the passenger connection was established as far as 's-Graven Voeren. But it did not take very long before the tunnel was no longer used for passenger transport. During the First World War, the line was dismantled by the German occupiers and the material was used for the construction of military equipment. After the war it was rebuilt, in 1920 to be precise, and trams were now used. At the start of the Second World War, the resistance used the tram to transport escapees. In 1942, history repeated itself and the Germans once again dismantled the line. The tunnel served as a weapons depot for the remainder of the war. In 1948 the line ended at Trembleur and in 1955 it closed for good. Only coal transport continued for a few more years. The rest of the tunnel's history is known. After its discontinuation, there was a period of decline and then the small tourist train until the disaster of 1991. After another period of decline and subsequent recovery, the tunnel is what it is today: among other things, a fascinating place with an intense past that wanders around in the sometimes cold wind that prevailed when we walked through.