The other day I was walking past a construction site in the Irvine Spectrum area, and noticed a rainbow-like ring appearing in the road. I immediately thought of this mystery photo on APOD and its (rather technical) explanation. Naturally, I had to take a picture myself.
It basically is a rainbow, except formed by reflections in tiny glass beads (used for sandblasting) instead of raindrops. The physicist who posted his (much better) photo to APOD had a better camera handy. And a linear polarizer. (Don’t you always carry one of those?)
Sadly, I only had my phone.