This one is our favorite! We explored the tunnel in 2004. For decennia it used to be the longest railway tunnel of Belgium. It has two separate tubes with at certain distances interconnecting galleries. That way it's possible to get from one to the other tube. The tunnel has a really fascinating atmosphere, with its flashes of light and weird air-movements.
The "Tunnel van Veurs" is part of railwayline 24. The Germans build this line as part of a fast connection between Germany and Belgium. Nowadays it's only used for freight, since there are only small villages in the area around the line.