THE Great Pyramid of Giza has just unlocked another mystery of ancient Egypt.
But what has become predictable for the pharaohs of old, the revelation is another mystery to unravel.
Scientists have discovered a hidden chamber in the ancient structure - one of the last surviving wonder of the ancient world - using cosmic-ray imaging, a technique that records the behaviour of subatomic particles called muons.
In an article published in the journal Nature, the international team said the hidden space was situated above the Grand Gallery, deep within the pyramid.
But what the chamber is or its purpose has completely stumped the experts.
"It could be composed of one or several structures," said Mehdi Tayoubi, a co-founder of the ScanPyramids project and president of the Heritage Innovation Preservation Institute.
"Maybe it could be another Grand Gallery. It could be a chamber, it could be a lot of things.
"The good news is that the void is there, and it's very big."
The Great Pyramid, also known as Khufu's Pyramid, has, along with its sister pyramids, been surrounded in mystery and is drawcard for travellers from around the world.
Scientists still debate over the construction of the pyramids, why they were built and, stoking some wild theories, the position of their sites.
And this latest discovery is sure to once again, stoke the flames of interest.