On a Wall In the Hallway Outside Our Airbnb in Madrid

I'm going to guess that the switch underneath this paper and tape does not turn on a light. 

I'll go farther: On one occasion at least, a visitor to the building has assumed that it did turn on a light, and therefore pushed it, and caused something undesirable to happen.

Just to be perverse, I gave it a good whack. The entire building collapsed around me.