Mirrors can be for so much more than just gawking at your slack-jawed mug first thing in the morning. They can, for example, be used to give the illusion that towering designs made of light reach out past you, to an indeterminable vanishing point seemingly so distant as to be infinitely far. That second one is what Carsten Nicolai is into.
Nicolai's installation Unidisplay provides just this effect. The wall upon which the lights are displayed is actually only 130-ish feet long, but the mirrors make it seem much, much longer. It's essentially the same effect you may have discovered as a child, perhaps in a department store dressing room, standing between two opposing mirrors. Except this time the mirrors are huge and there's also crazy rave-wall.
The piece is currently on display at the hangar Bicocca in Italy, so most of us are out of luck when it comes to seeing it. You could probably approximate the effect in your bathroom mirror if you've got a hand mirror lying around, but I'm betting it won't quite be the same at that scale. [HangarBicocca via My Modern Metropolis]