I though Switzerland's defense was more based around being mountainous and having explosives planted in critical tunnels/bridges and having a large percentage of the population armed and trained for national self defense. Basically in a ground invasion would be deadly and slow with no mobility and resistance everywhere.
Besides that it's hard to imagine which foreign power would have incentive and power projection to even try it.
The way I've understood it is that none of their defense is hidden, it uses the natural and societal benefits. Most of that could be gleaned by anyone with access to satellite images and wikipedia.
That might all be outdated info though, it'd be interesting to see where I'm wrong though!
Historically that has been the case for for Sweden as well I think. Every older apartment building I've lived in (built before 1990-ish) has had bunkers in the basement, and usually it seems to be sized for more than just the buildings residents (although it is repurposed for storage these days). Thick steel doors and all the other tell-tales of old civilian bunkers.
I'm guessing other European countries did this too.
I've definitely seen clips of heavy artillery tucked away into friendly barns and garden sheds. Maybe there's just wealthy people who like to collect large guns and there's some pride in turning away a Nazi invasion with their defenses.
Here's a cute video I found discussing the line of 12 fortresses protecting a little bottleneck of a river valley - he explains that the two camouflaged as villas are done so as not to be eyesores for the tourists.
A former infantry bunker is camouflaged as a medieval house in the town of Duggingen. Notice the half-circle windows, which appear to have been painted on
Nearby mountains have been made so porous that whole divisions can fit inside them. There are weapons and soldiers under barns. There are cannons inside pretty houses.
If you look closely, you can see a massive door in the hillside that would swing open - A Swiss Air Force Mirage III RS outside its mountain hanger.
Besides that it's hard to imagine which foreign power would have incentive and power projection to even try it.
The way I've understood it is that none of their defense is hidden, it uses the natural and societal benefits. Most of that could be gleaned by anyone with access to satellite images and wikipedia.
That might all be outdated info though, it'd be interesting to see where I'm wrong though!