A HUGE void has been found in the Great Pyramid of Giza in a discovery which could unlock millennia old secrets of the mysterious structure.
Despite studying one of the most impressive monuments in the world for centuries, archaeologists are still unsure how the Great Pyramid, which stands at 146 metres tall, was built.
But they have now moved one step closer to understanding the structure after discovering a “plane-sized” void in the middle of the pyramid.
Researchers announced the discovery on Thursday but said they did not know the purpose, contents or precise dimensions of what they are calling a "void" or "cavity" inside the pyramid, built as a monumental tomb around 2560 BC.
The discovery was made as part of the “ScanPyramids” project, which is using cosmic-ray imaging to map the interior of the great structures of Egypt.
To peer inside the pyramid, the scientists used an imaging technique called muon tomography that tracks particles that bombard Earth at close to the speed of light and penetrate deeply into solid objects.
Experts used muon technology which looks at muon particles that fall from the Earth’s atmosphere and usually pass through vacant spaces, but are also absorbed or deflected by harder surfaces – hence why the experts are capable of looking inside the pyramid without entering.
They said the newly discovered internal structure was at least 100 feet long, and located above a hallway measuring about 155 feet long called the Grand Gallery, one of a series of passageways and chambers inside the immense pyramid.
The researchers said it constitutes the first major inner structure found in the Great Pyramid since the 19th century.
Mehdi Tayoubi, a co-founder of the ScanPyramids project and president of the Heritage Innovation Preservation Institute, said: "This structure is not accessible, we don't see (that) people tried, if you look at the Grand Gallery, to access the void which is above.
"So this void was hidden, I think, since the construction of the Pyramid, it was not accessible.
"We needed this technique - the right technique at the right time - to be able to identify it and discover it.”
The discovery opens up the possibility that the void could be linked to other structures within the Great Pyramid, which was built for Pharaoh Khufu and completed in around 2550 BC.
Mehdi Tayoubi said: "What we are sure about is that this big void is there, that it is impressive, that it was not expected by, as far as I know, any kind of theory,"
”This is a premier.
"It could be composed of one or several structures... maybe it could be another Grand Gallery. It could be a chamber, it could be a lot of things."
"It was hidden, I think, since the construction of the pyramid.”
Hany Helal of Cairo University said: "We open the question to Egyptologists and archaeologists: what could it be?"
The Great Pyramid, looming alongside other large pyramids, was constructed during the reign of the Pharaoh Khufu, or Cheops.
It soars to a height of 479 feet, the tallest structure built by humankind until the Eiffel Tower in Paris in 1889, and boasts a base measuring 754 feet.
Muon particles originate from interactions between cosmic rays from space and atoms of Earth's upper atmosphere.
The particles can penetrate hundreds of yards into stone before being absorbed. Placing detectors inside a pyramid can discern cavities within a solid structure.