I'm always fascinated by rainbows and other phenomena where light is split into its component colours. While strictly not astronomical iself, the splitting of light into its component parts allows us to understand what stars are made from, and helps us find exoplanets. As well, finding these marvellous splashes of light keeps me attuned to the world around us.
When I saw these colourful splashes appearing on the floor of the Metro in Kongens Nytorv (which I always mispronounced as Koenigs, well Kongen does mean King as does Koenig), I was entranced, and started looking about for the door or window that had accidentally acted as a prism.....and found the deliberately placed prisms.
The light wells in the roof of the metro have a series of prisims specifically to catch light and send rainbows cascading down on the metro travellers. How could you not love a city like that!
Left image another rainbow in the stairwell, right image, the spiral of prisms in the light well.