A set of dramatic images has changed the Giza debate. They appear to show shafts, chambers and corridors extending far below the pyramids, perhaps even an interconnected system beneath the plateau. The maps come from Filippo Biondi and the Khafre Research Project, using a technique described as synthetic aperture radar Doppler tomography.

The claim deserves more than a quick dismissal. Biondi is not simply pointing at an ordinary satellite photograph and calling shadows a city. He has developed a signal-processing method, published earlier work on the Great Pyramid and presented tests on known structures. But the scale of the newer claims is extraordinary, and the evidence supporting them is not yet at the same level as the best-established discoveries made by ScanPyramids.

This is where the controversy actually begins: not with a choice between belief and disbelief, but with two very different ways of turning invisible signals into an image.

What Biondi’s team says it can see

In public presentations beginning in 2025, Biondi and colleagues described repeated SAR observations of the Giza plateau. Their reconstructions have been interpreted as large vertical or spiral-like structures beneath the Pyramid of Khafre, huge chamber-like forms at depth, and additional features beneath Khufu, Menkaure and the Sphinx. Later presentations suggested that some anomalies may form a wider, connected system.

Those are the “big voids” and hidden corridors now spreading across social media. In the strongest versions of the story, the Giza monuments sit above an engineered underground complex rather than a collection of isolated tombs, shafts and natural cavities.

That conclusion has not yet been demonstrated. A processed tomographic volume is an interpretation of measured signals, not a camera view through rock. The images may contain genuine information, processing artefacts, geological boundaries, model assumptions—or a mixture of all four. Calling a shape a corridor is already a step beyond detecting an anomaly. Calling several shapes an interconnected, human-made network is a much larger step.

The 2022 paper behind the technique

The foundation is a 2022 Remote Sensing paper by Filippo Biondi and Corrado Malanga. It openly acknowledges the basic problem: conventional radar waves have poor penetration through solid stone. The proposed solution is not to treat satellite radar as a direct underground flashlight.

Instead, the method analyses extremely small surface movements captured in coherent SAR data. Buildings and geological structures are never perfectly still. Background seismic activity, wind, temperature changes and other forces make them vibrate. Biondi’s approach attempts to extract those micro-motions and reconstruct the internal or subsurface structures that may be shaping the response.

The paper processed data from Italy’s COSMO-SkyMed satellites and reported a three-dimensional reconstruction of known and proposed features in and below Khufu’s pyramid. This is the serious core of the work. It is also why the debate cannot honestly be reduced to “satellite radar never penetrates rock.” Direct electromagnetic penetration is not the mechanism being claimed.

But an indirect method creates its own challenge: the answer depends heavily on the model connecting surface motion to hidden geometry. The deeper and more detailed the reconstructed object becomes, the more important calibration, uncertainty estimates, open processing steps and independent replication become.

How ScanPyramids is different

ScanPyramids uses cosmic-ray muons. These naturally occurring particles pass through stone, but dense material absorbs more of them than empty space. Detectors count how many arrive from each direction and build a density map. A surplus can indicate a void along that line of sight.

In 2017, the collaboration reported the ScanPyramids Big Void above the Grand Gallery. The Nature paper describes a space at least 30 metres long. Most importantly, the signal was reproduced with three different muon-detector technologies and three independent analyses.

A separate corridor behind the north-face chevrons followed. In 2023, muon measurements constrained it to roughly nine metres long with a cross-section around two by two metres. Ground-penetrating radar and ultrasound then helped localise the shallow feature, and later electrical-resistivity work provided another type of evidence.

This does not make every ScanPyramids interpretation final. Muography also produces density information rather than a normal photograph, and the purpose of a void cannot be read from particle counts. Its advantage is the chain of confirmation: multiple detectors, teams and follow-up methods converged on bounded anomalies.

Why the huge underground network remains controversial

The newer Khafre and plateau-wide maps are much more ambitious than the 2022 Khufu study. They move from reconstructing a monument to inferring detailed forms hundreds of metres or more below a geologically complex plateau. As of August 2026, the project has discussed a longer paper and independent confirmation, but the complete plateau-wide claim has not appeared as a fully documented, peer-reviewed result with open-enough data and methods for unrelated teams to reproduce it.

That matters for five reasons:

• Depth: a kilometre-scale inference is not equivalent to finding a shallow anomaly. Signal loss, geological complexity and possible surface-motion sources all increase.
• Resolution: a mathematically sharp reconstruction can look more certain than the underlying measurements. Every inversion needs a clear account of uncertainty and possible alternative solutions.
• Ground truth: known chambers are useful calibration targets, but recovering them does not automatically validate every unfamiliar feature at every depth.
• Independence: the most convincing confirmation would come from a separate team using separate data and processing, ideally supported by muons, seismic surveys, resistivity or carefully placed borehole instruments.
• Interpretation: even a genuine cavity might be natural karst, a fracture, an ancient quarry or a later tunnel. Geometry alone does not prove date, builders or purpose.

Conventional ground-penetrating radar offers a useful reality check. In blocky limestone at the Great Pyramid’s north face, a 2023 non-destructive testing study reported only about two metres of effective penetration at 200 MHz. Biondi’s method is different, but that comparison shows why claims of exquisite detail at enormous depth require unusually strong validation.

What would count as confirmation?

A responsible test should start with predictions made before new measurements are collected. The SAR team could specify the location, depth, size and expected orientation of a small number of anomalies, including uncertainty bounds. An independent group could then target the same coordinates with a method based on different physics.

Muon telescopes are already being developed for Khafre. Seismic tomography and electrical resistivity can search for density and conductivity contrasts, while gravimetry may help with very large cavities. None of these tools alone is magic. Together they can reduce the risk that one processing pipeline is drawing a persuasive structure from ambiguous data.

If several methods converge, the next step could be a narrowly targeted borehole or micro-camera investigation authorised by Egyptian authorities. A single confirmed chamber at a predicted depth would dramatically strengthen the method. Repeated failures would be equally informative.

Curiosity does not require premature certainty

The Giza plateau already contains known shafts, tombs, passages, quarries and natural geological features. More undoubtedly remains undiscovered. The debate is not about whether the ground is empty. It is about whether the specific, enormous network in the SAR Doppler reconstructions is real and whether its shapes have been interpreted correctly.

Biondi’s proposal is interesting precisely because it is testable. Its 2022 publication provides a method to examine rather than a rumour to repeat. The newer claims, however, must earn their certainty through replication.

For a wider explanation of what muons, radar, resistivity and other non-invasive tools can actually detect, see our guide to subterranean anomalies in modern archaeology. The most exciting outcome at Giza would not be one side winning an argument. It would be several independent instruments pointing to the same hidden place.