Istvan Orovitz's Anamorphic Art.

This one is called Jules Verne's Mysterious Island by Istvan Orovitz. At first glance, the image looks like a shipwreck on a weird-looking island. When a cylinder is put on the print, the reflection looks like Jules Verne!

A great (and famous) example of anamorphotic art (from Wikipedia):

In other anamorphisms, an anamorphoscope (a conical or cylindrical mirror) is placed on the drawing or painting to transform a flat distorted image into a three dimensional picture that can be viewed from many angles. The deformed image is painted on a plane surface surrounding the mirror. By looking uniquely into the mirror, the image appears undeformed. Current in the XVIIth and XVIIIth centuries, this process of anamorphosis made it possible to diffuse caricatures, erotic and scatologic scenes and scenes of sorcery for a confidential public. Anamorphoscopes were invented in China and brought to Italy in the 16th century, about the time Renaissance artists like Leonardo da Vinci were mastering 3-D and discovering slant anamorphosis.

Link (Thanks Vurdlak!) | Istvan Orovitz: Link | Anamorphic Art Link 1 and Link 2