Closed doors leave our imaginations free to wonder / wander.
We know that doors have a way of hiding what really is, preserving all along the veneer of normality, or wealth, or tidyness that is conveyed from the outside.
When we open doors and look inside, the veneer doesn't always (or often) correspond with the internal reality.
These guys in Germany offer a nice critique of that with a pretty special piece of silliness. They take the biggest door in the house, and offer their take on "I wonder what's inside?"
Of course, we are all still left wondering what really is inside behind their veneer-upon-a-veneer!