I have always been fascinated by optical illusions and was delighted to find this one right outside my front door in Celebration (well, balcony, it's an apartment). The illusion is produced by shadows on the bricks, the shadows coming from stairs that spiral round the outside of the building (you can see the building, courtesy Google Street View here). At least for my eye, the effect is quite startling.

You can only see it at certain times of day and certain times of year. At the moment, for example, the sun doesn't get high enough for the effect to show.

I wonder why these images are so compelling? Perhaps they serve as an ironic reminder of how fragile our grasp of reality is. Plato has us living in a world of shadows, rarely if ever seeing things for what they are. I like Fitzgerald's translation (another shadow) of Omar Khayyam

For in and out, above, about, below,

'Tis nothing but a Magic Shadow-show,

Play'd in a Box whose Candle is the Sun,

Round which we Phantom Figures come and go.