In terms of sheer size, Russia is the largest country in the world. That must have something to do with this gargantuan advertisement found in Russia... According to the caption, the surface area measures more than 1.5 acres (billboard haters should stop complaining right about now, as it appears we have it pretty good over here).
More interesting than the sheer massiveness of the super-colossal ad are the full-sized BMWs, lights ablaze, mounted sideways as if zooming across the surface. Those aren't base model Bimmers, either -- sharp eyed readers will recognize them as the Z4 M Coupe, M3, M5, and M6.
Source: http://www.autoblog.com/2008/04/01/bmw-builds-big-ad-in-moscow/