Bringing absolute terror to small children and dogs yet striking all others with awe, this tricksy street art is worth getting confused over.
If you happen to be in Stockholm this week then get yourself to Sergels torg, the most central square, and stare in amazement at Erik Johansson's handiwork.
The 3D illusion, entitled 'Mind Your Step', makes us believe that there's been some sort of summer blockbuster style disaster/alien invasion/robot war which has led to this cavernous hole.
It's a brave move for such a central space. We're up for equally apocalyptic pieces over here but we can't imagine The Daily Mail seeing the funny side.
You can see more of Erik's work here.