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?
1. The Helicopter Hieroglyphs in the Temple of Seti I
The magnificent great Pyramids of Giza are popular fodder for conspiracy theories and the whole of the ancient Egyptian civilisation has in one way or another been linked to bizarre alien conspiracies.
But one of the most convincing bits of evidence aliens have in fact helped raise the ancient civilisation is a set of unusual hieroglyphs in the 3,000-year-old Temple of Seti in Abydos, Egypt.
Among conspiracy forums, the icons have become known as the “Helicopter Hieroglyphs” for supposedly showing eerie pictures of what appears to be a helicopter and futuristic aircraft.
Some pseudo-archeologists who have seen the glyphs in person claimed they were left behind by time travellers while other suggested they were left behind to honour alien visitors.
Most genuine archeologists however will agree the icons are the simple result of typographical errors – overlapping symbols in a day and age where typos were quite literally set in stone.
Egyptian mystery: These hieroglyphs appear to show helicopters and space ships
Ancient alien evidence? Some believe the Charam mural depicts a UFO
2. The UFO ancient murals of Charama
This bizarre looking painting found in a cave in India has baffled scientists for its supposed depiction of an alien UFO beaming in the sky.
The fan-like antenna and the three legs of the vehicle’s stand clearly show a similarity to UFO type craft
The puzzling mural from Charama, Chhattisgarh, dates back some 10,000 years to a time before humans have invited the wheel.
Archaeologist JR Bhagat who studied the cave paintings in 2014 argued they were concrete evidence Aliens have walked among us in the past.
He said: “The findings suggest that humans in prehistoric times may have seen or imagined beings from other planets which still create curiosity among people and researchers.
“Extensive research is needed for further findings. Chhattisgarh presently doesn’t have any such expert who could give clarity on the subject.”
He added: “The fan-like antenna and the three legs of the vehicle’s stand clearly show a similarity to UFO type craft.”
3. The alien astronaut rock murals of Val Camonica
The rock carvings in the Alpine valley of Val Camonica, Italy, are one of the world’s largest collection of prehistoric petroglyphs.
Most of the glyphs were carved out some 8,000 years before the Bronze Age, and typically depict the everyday trappings of early man, such as scenes of people and animals.
But a set of particular carvings has convinced conspiracy theories some of the glyphs represent alien astronauts walking among them.
The glyphs in question appear to show men with radiating helmets on their heads, wielding oddly shaped weapons – perhaps in battle.
UFO hunters from around the globe believe these images to be indisputable proof.
Bizarre theory: Some think these etchings depict alien astronauts
Anciet Assyrian: Conspiracists think this is an image of an alien spaceraft
4. Mysterious winged object on the Palace of Ashurnasirpal II, King of Assyria
A piece of stone panel on the walls of the once mighty ancient palace contains the depiction of the Mesopotamian god Ashur inside of an orb with outstretched wings.
Although the stone carving clearly harks back to ancient Mesopotamian religious beliefs, some conspiracists believe this depiction of Ashur to be that of an alien traveller.
One UFO conspiracist going by the username of Luissaade, claimed the embossment is “early man’s way of drawing alien beings that were seen pilots flying machines, alien high technologies, on Earth.”
The Palace of Ashurnasirpal II, or the Palace of Kalhu, is an ancient site dating back to 879 BC in modern-day Iraq, just north of Baghdad.
Most of the palace was excavated in the 1840s by British archeologists, with its stunning findings found in museums across the planet today.
Alien spacecraft: This Mayan sarcophagus lid supposedly depicts a space traveller
5. The bizarre sarcophagus lid of Mayan king Pacal
Ancient Mayan artwork is known for its intricately detailed, weaving and geometric designs and the sarcophagus lid of the Mayan king Pacal is a testament to the Mayan’s prowess.
However the 1968 book Chariots of the Gods, by Erich von Däniken, has pointed out that far from being an extremely lavish coffin, the sarcophagus contains references to alien UFOs.
According to Mr von Däniken, the central figure in the middle of the sarcophagus is an extraterrestrial alien riding what appears to be a rocket or some sort of space ship control centre.
He wrote: “In the center of that frame is a man sitting, bending forward. He has a mask on his nose, he uses his two hands to manipulate some controls, and the heel of his left foot is on a kind of pedal with different adjustments.
“The rear portion is separated from him; he is sitting on a complicated chair, and outside of this whole frame, you see a little flame like an exhaust.”