Follow the movement of the rotating pink dot with your eyes and the dots will remain only one color, pink. But if you stare at the black + in the center, the moving dot will turn green.

 

the classic

 

This one by M.C. Escher hangs in my study
I actually made a jig that I can use to cut out the cubes on top of the towers, using a table saw.

 

if you look close none of this is moving