We visited the tunnel in april 2006. It was terrible weather, rainy and very cold. We camped on a hill near Aachen. You could hear the sound of the trains roaring up the hill. The tunnel has a third track for higher trains. Somehow the light in this tunnel was continuously shining in our faces, very irritating. We had to use our flashlights in order to be able to see. Because of the hill following the tunnel you couldn't see any trains coming... The tunnel is placed almost directly below the "Drielandenpunt". It's not really exciting.
In 1862 a German railway company BME wanted its own connection to Belgium in order to earn a market share in the busy traffic between the two countries. In 1870 work began building the Gemmenicher tunnel or Tunnel van Botzelaer (the Belgian name) as part of the new line between Aachen and the mines of Plombières, in that time known as Bleyberg. This village was situated in a neutral stateless triangle between Belgium, Germany and The Netherlands. In 1872 the German railways got nationalised as a result of the Franco-German war. After the first world war the Belgian border shifted to halfway the tunnel. In 1968 the German part of the line (till halfway the tunnel) got electrified, the German calculated it was cheaper to use electric locomotives. It remains a mystery why the Belgians still didn't come to the same conclusion. Nowadays the line is under the administration of line 24 and has only freight traffic.