I know their scientific explanations and--actually I know a whole lot about light and the electromagnetic spectrum now, but unlike some things, the more I learn about rainbows the more fascinating I find them to be. All the more so because they are so rare and nearly impossible to recreate--on the sky-arching scale. Actually, I'd say they were impossible to create artificially, but if I do I'll see a news article about man-made rainbows tomorrow, so never mind that.
I think one of the most curious things I learned about rainbows is that they are actually circles, and not just arches. You can't see the whole thing unless you're in an airplane (although I wonder if a mountain view will let you see it), but there were a few pictures along with the explanation, and it was a whole circle cast across the landscape, which is a totally awesome idea.
And really leaves you wondering because that means the rainbow touches the earth in a certain place, so would that be the end of the rainbow? or not, since the rainbow doesn't actually end there?