From the raising of the Egyptian pyramids to the mysterious Nazca Lines and the ominous heads of Easter Island, the creation of many ancient constructions has been attributed to interstellar visitors.
For decades, these impressive man-made sites have been scoured by crypto-archeologists in the hopes of discovering evidence of extraterrestrial intervention.
Over the years many claimed to have uncovered concrete proof of ancient carvings, cave paintings and other iconography that is indisputable proof of UFOs.
But what are some of the most convincing of these supposedly alien depictions from a time long past?