Fixate the red point you will see in the center while paying attention to the rotating ring of gray lines
Most observers perceive that the ring of lines rotates slowly, with brief jumps of much faster rotation in the opposite direction. The very fast jumps are illusory. The illusion usually gets stronger after one or two jumps, and seems to be enhanced by paying close attention to the lines in the ring.
The most famous illusion of movement is the motion aftereffect: look at uniform motion for a while, and things will seem to move the other way. It was discovered a long time ago by staring at a waterfall in Scotland, and, though important, is a bit boring: the illusory motion is slower than the real movement that induces it. As it turns out, the Scottish waterfall actually feeds… Loch Ness, and that just under the placid surface of the motion aftereffect lurks a true monster, capable of producing illusory motion a hundred times faster than the inducing movement.