@meesterboom spoiler alert - hahah
I looked at it again and I think I found the answer - the trick is making it "spiral"
the paper was not and cannot (unless I treat it or use boards instead) make the same optical illusion cause it cant be made spiral :D
The artist is a freaking genius to have made his metal artworks do the trick I had to insist I should write about him and he was very kind and with a big heart he said "yes - I may" in German - I only heard "dat mach?" "Dat mag?" anyway, until hub said yes - I couldn't :D