What? No, seriously. This morning, overhead by the river, a gorgeous, clear, and long-lasting circumzenithal arc. I learned about these from Urban Naturalist, though I'd never seen one. They happen when the ice crystals in cirrus clouds are properly aligned. It looks like a partial rainbow curving in the sky, not anchored in the ground. This is similar to what I saw, though not taken by me. Moral: when there are cirrus clouds, look up!