You can see one such image in the Wiki about autostereograms,
I suddenly thought of them now when thinking about the Spinning Dancer illusion, and I decided to...what else...google for them.
If you have not "seen" an autostereogram before, there is a technique to it. What works for me is seeing "into" the page, focusing just beyond the printed pattern; quite suddenly, the hidden picture comes into three-dimensional view against the background. Sometimes, though, the hidden picture can be "set into" what becomes the foreground.
are a series of these images....I intend to have fun for a while....I hope you do, too! Alas, a few of my friends were never able to "see" the hidden picture..I hope you are not among that number!