This week’s image comes from Florence, Italy — it’s of a model (made by a local artist) from one of Leonardo da Vinci’s more famous drawings:
Leonardo da Vinci left behind a wealth of sketches — some were of purely artistic content, while others were part of his process of puzzling out how things work. His drawing of an “air screw” was probably intended as such a conceptual tool. While its implementation is far too heavy to ever fly (particularly when human-powered), you can see in it the seeds of concepts behind modern helicopters.
I ran across this exhibit of models of da Vinci “inventions” while I was in Florence for other reasons. But since so many of da Vinci’s sketches are easily built (if not always practical), it’s usually not too difficult to find a similar exhibit on your own travels.