When it comes to admiring 3D street art, it's often a matter of perspective -- look at a street artist's design from one angle and it appears flat and distorted, but from another the illustration comes alive.
The process is called anamorphosis, and requires the viewer to stand at a certain vantage point in order to view the three-dimensional image. The optical illusions have been popping up around the world from London and Spain to New York and Denver.
While some street works of art are more advanced than others, one thing stays the same -- the perception of depth in a (technically) two-dimensional illustration.
See some of our favorite picks of 3D street art from around the world in the gallery below, and let us know your thoughts in the comments section.