Two small voids found behind Menkaure's granite cladding raise fresh questions about the pyramid's design
Scans of the Menkaure Pyramid, the smallest of Giza's three main monuments, have revealed two unexpected air-filled cavities directly behind its polished granite casing on the pyramid's eastern face. The discovery was reported by a team led by archaeologists Khalid Helal and Mohamed Elkarmoty of Cairo University and published in NDT & E International.
These anomalies follow earlier high-profile discoveries inside the Great Pyramid of Khufu — including a large internal void and a corridor — but the Menkaure cavities differ markedly in shape, size and layout, suggesting a different construction process or purpose.
"The images revealed two anomalies directly behind the polished granite blocks, which would indicate the presence of air-filled voids," the team writes, adding that numerical simulations supported that interpretation.
How the voids were detected
To avoid damaging the four-millennium-old monument, the researchers used non-invasive geophysical methods as part of the ScanPyramids project, co-led by Cairo University and France's Heritage Innovation Preservation Institute. Three complementary techniques were applied:
- Electrical resistivity tomography (ERT) — measures how electric current flows through materials to reveal resistivity contrasts;
- Ground-penetrating radar (GPR) — sends radio waves into the masonry and records their reflections;
- Ultrasonic testing (UT) — uses sound waves to detect differences in internal structure.
All three methods independently flagged two small anomalies that did not behave like surrounding limestone or simple mortar joints. The larger anomaly was located about 1.4 metres beneath the granite cladding and measured approximately 1.5 m wide by 1.0 m high; the smaller sat at about 1.1 metres depth and measured roughly 0.9 × 0.7 m. Numerical simulations that tested alternative explanations — such as blocks of stone with different physical properties — were unable to reproduce the observed signals, strengthening the air-void interpretation.
What it might mean
Unlike the Khufu discoveries (one of which is very large and another that appears structurally organized), the Menkaure voids are small and irregular. The researchers note that the pattern of granite blocks covering these anomalies resembles the block arrangement around Menkaure's northern entrance. Independent researcher Stijn van den Hoven suggested in 2019 that that block arrangement could indicate a second entrance — a hypothesis that the new data makes worth re-examining.
However, the team could not determine how deep the cavities extend with the present methods. They recommend follow-up imaging using cosmic-ray muography (muon imaging) to map the cavities' depth and internal geometry, and they urge broader discussion of the findings among Egyptologists before drawing definitive conclusions.
Context: Menkaure was last excavated in detail by George Reisner between 1906 and 1910. Its partly unfinished reddish granite casing over a limestone core distinguishes it from the larger Khufu and Khafre pyramids and hints at shifting priorities during construction. The new non-invasive findings add a fresh chapter to ongoing research into ancient Egyptian building techniques and the internal architecture of the Giza monuments.
Publication: The study appears in the journal NDT & E International.
