Massive 2,600-year-old Egyptian structure found beneath Nile Delta using satellite radar

The site, known as Buto, was one of the most important religious centers in pharaonic Egypt, dedicated to the cobra goddess Wadjet. While archaeologists have excavated its upper layers for decades, reaching remains from the Ptolemaic and Roman eras, the deeper, waterlogged layers had remained inaccessible, until now.

By analyzing radar images from the European Space Agency’s Sentinel-1 satellite, researchers spotted a large oval-shaped anomaly beneath a mound called Kom C, measuring 420 feet long and 203 feet wide (128 by 62 metres). Electrical resistivity tomography (ERT) profiles were also used to map the walls of the mudbrick structure.

The study, published in Acta Geophysica, revealed a layered history. Scattered Ptolemaic and Roman debris sat in the top 10 feet. Beneath this, between 10 and 20 feet deep, lay the large Saite-era mudbrick structure, possibly a tomb, priest’s house or shrine. Dating was based on the archaeological layer, brick shape and artifacts such as pottery, with carbon-14 dating applied to associated organic material.

But the most surprising find came even deeper. Between 20 and 23 feet (6 to 7 metres) underground, the researchers found a thick, clean layer of sand placed deliberately beneath the building’s mudbrick walls. “Using pure sand as a stabilizing cushion was a brilliant, deliberate tactic — the ancient builders profoundly understood their environment,” Hussein Bassir, director of the Antiquities Museum at Bibliotheca Alexandrina who was not involved in the study, told Live Science.

The Nile Delta’s clay is notoriously treacherous. It absorbs moisture and swells, then contracts and shifts as it dries. The sand cushion would have distributed the building’s weight, allowed groundwater to drain and stopped the clay from creeping, following the same engineering logic as modern load-distributing foundations.

“By combining satellite radar with deep ERT profiles, we didn’t just map the walls of this massive Saite-era structure — we were also able to analyze the subsurface layers,” said study co-author Abdelaziz Elfadaly. “The detection of a significant, clean sand foundation layer beneath the mudbrick walls explains how these heavy structures survived the high water table and shifting clayey soil of Buto.”

A confirmation trench excavated down to the sand layer uncovered thick mudbrick walls resting on it, as well as artifacts pointing to the site’s sacred function. These included ushabti and shawabti figurines, small servant statues for the afterlife, and a limestone altar with channels bearing dried residues consistent with animal blood. A rarer find, a faience baboon figurine associated with Thoth, the god of wisdom, was also recovered.

The Saite period (26th Dynasty) was a time of cultural revival after generations of Assyrian and Libyan domination. The pharaohs, ruling from the nearby Delta city of Sais, poured resources into restoring the region’s religious landscape. Buto, a focus of Lower Egyptian identity, was a natural priority.

The team is now planning a return visit with wider electrical resistivity surveys to reach deeper layers, along with specialists who study ancient plants and how geological features changed over time, which may help reconstruct the landscape as it was when these walls were first laid.