Deep under Luxembourg City lies a 900 metre tunnel. No records are said to exist for its construction but it is construed that it was originally constructed as a storm drain but had also been identified as a potential nuclear shelter.
The tunnel runs from the Petrusse Valley right beneath the capital and emerges close to the Vauban Towers. It measures around 3.5 metres high with a width of 5 metres. Signage inside occasionally refers to the names of the streets that are on the surface immediately above.