A Whatever Works Away Day at the Technical Museum in Vienna. https://www.technischesmuseum.at/language/en-us/home
This is the best science museum I have ever visited. It focusses more on technology than pure science. At the moment it doesn't have any exhibits of IT tech, but major renovations are taking place.
However, if you want to know about how just about anything else works, this is the place to go. It covers stuff from basic science (mass spectrometers, early experiments to determine the atomic weight of molecules), to heavy engineering. There is a Bessemer Converter, trains, machines for pressing steel. The list is almost endless.
There is a very good children's section and lots of interactive machines to demonstrate various physical principles. It's huge, so you need more than one day if you want to explore it all.