Behind the scenes tours in Zürich

I usually enjoy visiting behind the scenes tours in factories, waterworks, water towers, industrial areas, airports, libraries, hotels, abandoned basements, caves or just closed old buildings etc. I have found that these places are mostly closed for public but sometimes they are accessible and it's a great experience if you can visit one.

We're going to Zürich for a few days in the next week and I'm looking for tours like these ones. Any tips?