Not sure how many contributions there will be, but I will drag out a few already made (if I can find them), to answer a question from Cesariojpn in another thread. Plus, it gives me another excuse to post my otherwise destination-less photographs. First we have the Spiral Bridge on 414, the Shimoda Highway on Izu:
Built we assume in place of the usual mountain-side switch backs, merely to gain / lose height down the central Izu road out of the mountains. A bit scary as you pass well out into space on the two full circuits. We guess it dates from sometime in the 1980s when spending money on domestic projects (to the value of the US defense budget) was a government objective here. Neko.