<a href="https://en.wikipedia.org/wiki/Fraser_spiral_illusion" class="extiw" title="en:Fraser spiral illusion">Fraser spiral illusion</a>. The eyes see a spiral, whereas the picture is made of circles.
<a href="//commons.wikimedia.org/wiki/User:Subsidiary_account" title="User:Subsidiary account">Trent Steel</a>, from on <a href="https://en.wikipedia.org/wiki/Fraser_spiral_illusion" class="extiw" title="en:Fraser spiral illusion">original concept</a> found by James Fraser in 1908.
2021-09-05
<span class="int-own-work" lang="en">Own work</span>