The Cydonia region of Mars is located at 41° north latitude, 10° west longitude on the red planet. It was photographed several times by NASA's Viking Mars-orbiting spacecraft in the mid-to-late 1970s. One ground object drew the attention of researchers because of its striking resemblance to a human face. In the opinion of many who have viewed the higher resolution images, the resemblance is closer than seems likely to have arisen by chance, despite half the "face" being hidden in shadow. Because it is a three-dimensional "face" and not just a profile, it has been described as the next best depiction of a human face in stone on its (~ 1 kilometer) size scale in the explored solar system after Mount Rushmore in South Dakota.

The "Face" on Mars has now passed each test of artificiality yet proposed. These tests include a three dimensional structure, a lack of fractal patterns in the image, non-random distribution of the nearby small mounds, proximity of other anomalous landforms, an apparent bilateral symmetry, being located on the martian equator, having a culturally significant orientation, and serving an apparent culturally significant purpose. It would be an exaggeration to say that the case for artificiality is now compelling, and many thoughtful people will still find that conclusion less likely than all these "coincidences" put together. Yet the balance of the evidence, considered objectively, now weighs clearly in favor of artificiality over a natural origin of the Cydonian landforms.