Impossible alphabets and fonts

Priori Acute is the result of a series of experiments into three-dimensional letter form design inspired by 19th Century display and artistic printing types. However, instead of simply adding drop shadows or fake relief to create the illusion of depth, the designers at Jonathan Barnbrook's studio took their cue from such diverse sources as the angles on the Stealth bomber and the visual conceit in the work of the Dutch graphic artist M.C. Escher.

The image was found http://www.emigre.com/EFfeature.php?di=214