I can't believe that in all these years, I never went to Musée des Arts et Métiers. It's a wonderful science museum that focuses on machines over the years, and doesn't have the hords of screaming kids, which is a huge plus :)
Most people don't know that the first heavier than air aircraft was french and dated from the late 1800's. It was however a poor aircraft that was not well controlable, so history didn't remember it as the first aircraft:
More interestingly, the museum is attached to a church was was repurposed as display space:
We ended up spending much longer than planned there, and it was worth even more. Greatly recommended.