This is What Happens When You Build a Cube Out of One Way Mirrors

Built and designed by Numen/For Use, N-Light Membrane is a giant cube with three out of the six surfaces made of flexible membrane (foil mirror) with an air tank and a compressor connected to it. 

The other three mirrors are semi transparent spy-glass. By inflating or deflating the air tank, the membrane turns convex or concave, deforming the reflections within.

More at Twisted Sifter.