It’s the first time I’ve seen one of these thought it appears they’re not that rare. A rainbow, photographed from our garden:
But it’s a double — there’s a second rainbow above it, just visible in this photo (most easily at the treeline and the edge of the picture):
And adjoining the first, underneath it, some additional refraction effects as well. I’ve seen quite a few double rainbows, but never noticed this before:
It’s very faint, but it’s definitely there.