Etsy seller ExoticTiles made this eye-watering optical illusion table out of hand-cut tiles. It's $500 plus your optometry and psychoanalyst bills. The effect is called a Café wall illusion.
This table is made from hand-cut and hand-glazed trapezoidal tiles. It comprises four concentric circles (believe it or not!) around a central disc. The way the brain processes contrast information causes one to perceive the circles as narrowing. Each circle contradicts the ones beside it.
Café Wall Illusion Table (Thanks, Kim!)
I write books. My latest is a YA science fiction novel called Homeland (it's the sequel to Little Brother). More books: Rapture of the Nerds (a novel, with Charlie Stross); With a Little Help (short stories); and The Great Big Beautiful Tomorrow (novella and nonfic). I speak all over the place and I tweet and tumble, too.