One evening in 1971, a Spanish woman looked down at her cement floor and saw what appeared to be a face staring back at her. Thus started the strange event in history known as the Belmez Faces:
She recruited her son and husband to get rid of the disturbing image. They took a pickaxe to the cement, removed the face, and poured new cement over the hole. However, after doing so, the face eventually reappeared, and went on to be accompanied by more faces throughout the house. Word spread, and the house became an area of great interest for paranormal enthusiasts and skeptics alike. Many regarded the phenomena as among the most bizarre and substantial cases of paranormal activity ever recorded (after all, so many visitors flocked to the house that the faces ended up being seen by countless people). Skeptics, on the other hand, were fairly certain that some form of trickery must have been involved.
Samples of the cement were taken, and over the years, they have been subjected to various studies. Although no obvious evidence of trickery has ever been found, studies have indicated that some slight traces
of chemical elements which may show that the faces were somehow painted onto the cement were found. Although many skeptics took this revelation as proof that the images had been faked, it should be noted that the process of creating them would still be intricate and, apparently, involve a strong knowledge of chemical compounds. The family that resided in the home did not seem to possess such knowledge.
What is even more notable about this particular case is that, over the years, faces have continued to appear in the home.
Read this and two more history of bizarre images over at Weird Worm: Link