A scan under the Great Pyramid revealed a hidden corridor no one had entered

For more than 4,500 years, the inside of the Great Pyramid of Giza appeared to be fully charted, its known passages and chambers explored and re-explored by generations of visitors. Then, without cutting or moving a single block, physicists found spaces that no one had known were there. By tracking cosmic particles that pass through solid stone, an international project detected hidden voids deep within the monument built for the pharaoh Khufu, including a corridor tucked behind the pyramid’s north face that no human being had entered since the structure was raised.

Reading a pyramid with cosmic rays

The technique behind the discoveries is called muography, and it borrows a tool from particle physics. When cosmic rays from space strike the upper atmosphere, they generate showers of subatomic particles called muons, which rain down constantly and can pass through large amounts of rock. Solid stone absorbs more of them than empty space does, so detectors placed inside and around a structure can record where extra muons are getting through and, over months of exposure, build up an image of the density hidden inside, much as a medical X-ray reveals bone against soft tissue. The ScanPyramids project began applying this approach to the Giza monuments in 2015, using layered detectors so that unexplained voids would show up as bright patches in the muon count without any need to drill or dig.

The “Big Void” found in 2017

The first major result came in 2017. That year, the team reported in the journal Nature the detection of a large empty space above the pyramid’s Grand Gallery, a feature they called the Big Void. According to the 2017 analysis, the cavity stretched at least 30 meters in length, making it the most significant internal discovery in the pyramid in generations. Its purpose was not clear, and the finding set off debate among Egyptologists, some of whom suspected it might reflect construction features, such as spaces left to relieve the weight bearing down on the galleries below, rather than a deliberate room. What was not in dispute was that a sizeable emptiness had gone unnoticed inside the most studied ancient building on Earth.

The north-face corridor, mapped in 2023

A second void, closer to the surface, was pinned down with far greater precision several years later. Researchers had noticed muon signals near the pyramid’s north face, behind a set of large chevron-shaped stones set above the original entrance, and follow-up measurements resolved the space into a defined corridor. In a study published in Nature Communications in March 2023, the team characterized it as roughly nine meters long and about two meters wide and tall, with a gabled ceiling formed by stones leaning against one another. Unlike the deeper Big Void, this corridor sat close enough to the exterior that its shape and position could be described in detail, and it lined up with the mysterious chevron blocks that builders had placed on the north face for reasons long unexplained.

A first look inside

Because the corridor lay just behind the outer stones, it also became possible to see into it. In 2023, investigators threaded a slender endoscope through a narrow joint between the chevron blocks and captured the first images of the space, confirming an empty, unfinished-looking passage with a vaulted stone ceiling. As coverage of the muon work described, the camera revealed a corridor that had been sealed off and unseen by human eyes since the pyramid’s completion, a hollow that the particle scans had located from the outside before anyone laid eyes on it. The endoscopy turned an abstract signal in the muon data into a concrete, photographed space.

What the corridor might be for

What the passage was meant to do remains an open question. The leading explanation is structural: a corridor of this kind could redistribute the immense weight of the masonry above the pyramid’s entrance, or above some chamber or feature still hidden deeper inside, preventing the stones from crushing the spaces below. Others have wondered whether it points toward as-yet-undiscovered rooms. The Great Pyramid was built during Egypt’s Fourth Dynasty, around 2560 B.C., as a tomb for Khufu, and its precise internal logic has never been fully recovered. What the recent work has shown is that non-invasive imaging can still surprise, adding real spaces to the map of a monument that seemed to have given up its secrets, and researchers have continued scanning in the hope of learning whether these newly found voids lead anywhere further.

Muon measurements cannot identify inscriptions, objects or the original function of a cavity. They reveal differences in density, and the resulting geometry must be compared with the pyramid’s masonry and known construction techniques. That limitation is also the method’s strength: competing explanations can be tested without opening a passage or disturbing blocks that have remained stable for millennia. Additional detector positions can sharpen the corridor’s outline, while thermal imaging and radar can examine the shallow stonework from other physical angles. Any proposal to enter farther must balance the information gained against structural and archaeological risk, making continued remote observation the most cautious path.

This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.

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