(Yes, that's Beck.)
I found it the idea on Curbly (a site you should definitely check out if you haven't already) though it was originally posted on Re-Nest (the green section of Apartment Therapy). The idea is to put whatever art you like in the mirror area and recess it into a wall so that you only see a framed picture. It's a secret cubby! Or extra storage for a minimalist space! Or hang up a series of three in the kitchen to use as a spice cabinet as suggested on Re-Nest!
The photo is from Flickr member JonnyXandtheGroadies, licensed for use by Creative Commons.
Link up below! (When entering your link, please take care to link to a specific project you have done, not your blog's main page. Thanks!)