They were not, so the polemic went, the work of ‘puny’ man, but instead those ‘giants of Mars’.
Yes, the Pyramids of Giza – those monuments to god-like splendour that have stood for more than 4,000 years – were built by aliens.
That was the ‘claim’ made by American astronomer Garrett P. Serviss in his 1898 book Edison’s Conquest of Mars.
Perceptive readers will have noted that Serviss’s work – an unauthorised re-write of HG Wells’ 1897 alien invasion novel The War of the Worlds – was fictional.
But it did popularise a theory that, even in more recent years, has continued to find traction.
In 2020, billionaire Tesla boss Elon Musk drew the scorn of experts when he took to Twitter – the social network that he bought in 2022 for $44billion – to write: ‘Aliens built the pyramids obv’.
Now, the discovery this month that an ‘underground city’ lies in a ‘hidden world’ beneath Egypt’s most famous pyramids has again focused attention on the structures that have obsessed experts and amateurs alike for millennia.
Just what could the vast network, which descends more than a mile into the sands, have been used for?
Musk’s comment five years ago prompted Egypt’s international co-operation minister to say that seeing the tombs of the pyramid builders would be the proof that aliens did not construct them.
Rania al-Mashat said: ‘I follow your work with a lot of admiration.
‘I invite you & Space X to explore the writings about how the pyramids were built and also to check out the tombs of the pyramid builders. Mr. Musk, we are waiting for you.’
Egyptian archaeologist Zahi Hawass also waded into the bizarre row, saying in a video that Mr Musk’s argument was a ‘complete hallucination’.
The largest of the three pyramids at Giza – the Great Pyramid – was built more than 4,500 years ago in around 2560BC for King Khufu, who was the second pharaoh of Ancient Egypt’s fourth dynasty.
Until the completion of Lincoln Cathedral in the 14th century, it was the tallest building in the world.
The pyramid, which was topped with a gold or electrum capping stone, was built as a sacred tomb for Khufu, who believed himself to be divine.
The other two pyramids, built for pharaohs Menkaure and Khafre, were constructed decades later.
The notion that the structures were built by or with the help of aliens gained further traction with Swiss author Erich von Däniken’s influential 1968 book Chariots of the Gods.
He argued that Giza’s Great Pyramid could not have been built without the help of advanced alien technology.
The author wrote: ‘If we meekly accept the neat package of knowledge that the Egyptologists serve up to us, ancient Egypt appears suddenly and without transition with a fantastic ready-made civilization.
‘Great cities and enormous temples, colossal status with tremendous expressive power, splendid streets flanked by magnificent sculptures, perfect drainage systems, luxurious tombs carved out of the rock, pyramids of overwhelming size – these and many other wonderful things shot out of the ground, so to speak.
‘Genuine miracles in a country that is suddenly capable of such achievements without recognizable prehistory!’
He added: ‘An artificial mountain, some 490 feet high and weighing 6,500,000 tons, stands there as evidence of an incredible achievement, and this monument is supposed to be nothing more than the burial place of an extravagant king!
‘Anyone who can believe that explanation is welcome to it…’
The late Belgian author Philip Coppens was similarly forthright in his 2011 book The Ancient Alien Question.
He said in one passage: ‘If aliens built the Great Pyramid, then it needs to be argued that they were also responsible for at least some of the other pyramids in ancient Egypt.’
But experts have rubbished any notion that beings from other planets might have been involved in the construction of the pyramids.
Speaking on the BBC’s History Extra podcast, British Egyptologist Professor Joyce Tyldesley said: ‘It’s almost almost sort of a bit like a form of racism, isn’t it, that these people couldn’t do it, so someone else must have done it.’
‘But I think there’s a bit more to it than that. Because prior to the idea of aliens helping build the pyramids, we had the idea that maybe people from Atlantis might have helped build the pyramids, and prior to that, we had the idea that God inspired builders to use the pyramid inch, a divinely inspired measurement to build the pyramids.
‘So I think it’s that there’s always been a long succession of theories about how the pyramids might have been built, and as one is sort of superseded by the other.
‘So it doesn’t just come out of nowhere. I think it’s a sort of changing and evolving belief as how the pyramids might have been built, and that’s just the latest one that we have.
‘As we become more interested in space and aliens, then they’ve sort of been attached to this theory as well.’
However, mystery over the pyramids’ construction remains.
The Great Pyramid was supposedly completed in 24 years.
But it was built from 2.3million limestone blocks, with each one weighing between 2.5tons 70 tons.
British writer Graham Hancock noted: ‘Assuming the masons worked ten hours a day, 365 days a year, they would have needed to place one block every two minutes.’
Writing more than 1,000 years ago, historian Abul Hasan Ali Al-Masudi invoked the notion of ‘acoustic levitation’ – the use of sound waves to make the blocks weightless.
Al-Masudi said that an inscription written on papyrus was slipped beneath each block.
When a note sounded, the stone would lift off the ground and then float into space.
The latest discovery that cavernous spaces exist beneath the pyramids was made by researchers from the University of Strathclyde in Glasgow and the Italian University of Pisa.
‘When we magnify the images we will reveal that beneath it lies what can only be described as a true underground city… an entire hidden world of many structures,’ said Corrado Malanga, one of the archaeological researchers.
It remains a mystery how much older than the pyramids the structures are.
It is also unknown was their purpose is, but they are connected by geometric passages.
Even more spectacular are eight vertical columns that descend 2,1245feet into a pair of huge chambers.
The depth is is almost five times the height of the Khafre Pyramid.
The cylinders are aligned in two rows of four that run north to south.
Given that the edges of the Great Pyramids face exactly north, south, east and west, the arrangements of the cylinders is certain to be significant.
And around each pillar is a staircase-like walkway.
The discovery of the underground structures piles further intrigue on a subject that is endlessly fascinating.
Scholars all over the world – and amateurs who follow every development avidly – will be waiting to see what findings emerge next.
For more than 4,500 years, Egypt’s pyramids have kept their secrets hidden deep within the labyrinth of passages and chambers that lie inside their towering stone structures.
But the long-running row over whether the Great Pyramid of Giza is hiding a network of previously undiscovered tunnels behind its stone walls has now been answered.
The researchers confirmed the find using cosmic particles known as muons to scan the Great Pyramid of Giza.
They used the scans to create maps to reveal the internal structure of the 479 feet (146m) high pyramid.
Last year thermal scanning identified a major anomaly in the Great Pyramid, the largest and oldest of the pyramids at Giza and one of the seven Wonders of the Ancient World.
Those scans identified three adjacent stones at its base which registered higher temperatures than others.
This led to theories that they may be hiding a secret chamber that had yet to be discovered.
A team of experts then set up the ScanPyramid’s project to use muons, tiny subatomic particle that are typically produced by cosmic rays smash into atoms on Earth, to peer through the Pyramid’s huge stone blocks, some of which weight up to 15 tons.
Dr Hawass has in the past been sceptical of the usefulness of conducting such scans.
He recently clashed publicly with British Egyptologists over their theory that a secret burial chamber may be hidden behind the walls of Tutankhamun’s tomb in his pyramid in the Valley of the Kings.