Satellite radar reveals a 2,600-year-old mudbrick complex buried beneath Buto in the Nile Delta

Found from space, then mapped from the ground

Buto was one of the most important religious centres of Lower Egypt, sacred to Wadjet, the cobra goddess and protector of the land’s rulers, with a history stretching back to the Predynastic period, around 3800 to 3100 BCE. Its mounds rise above the Delta plain, but the deeper occupation layers have long been out of reach: later Ptolemaic and Roman settlement piled up above earlier buildings, and groundwater and waterlogged Nile Delta clay make deep excavation difficult. The team, led by researchers from Kafr el-Sheikh University and Egypt’s National Authority for Remote Sensing and Space Sciences, turned to methods that look underground without digging. They processed a Sentinel-1 radar image captured on 5 May 2018, which revealed the oval anomaly beneath Kom C. They then ran 15 parallel electrical resistivity tomography surveys across about 5,400 square metres, sending currents through the ground and measuring how they moved, and built a three-dimensional model of what lay below.

The model showed a large rectangular mudbrick structure measuring about 20 by 25 metres, with substantial walls up to 5 metres thick and evidence of an associated enclosure, lying 3 to 6 metres below the surface. The upper three metres held scattered mudbricks, pottery and limestone fragments from Ptolemaic and Roman occupation; the Saite-period architecture lay beneath them. The researchers date the structure to the late eighth century BCE or the Saite period, the 26th Dynasty, which ruled Egypt from about 688 to 525 BCE.

A sand foundation laid on purpose

The most surprising find lay deeper still. At about 6 to 7 metres down, the surveys identified a thick layer of relatively clean sand beneath the mudbrick walls. Boreholes show that natural sand occurs considerably deeper beneath Buto, so the researchers conclude the shallower deposit was deliberately introduced — an artificial foundation under the building. Such a bed could have spread the structure’s weight, improved drainage and kept groundwater from rising directly into the mudbrick walls. Study co-author Abdelaziz Elfadaly said the discovery could explain how substantial mudbrick architecture survived despite Buto’s high water table and unstable clay-rich sediments. Hussein Bassir, director of the Antiquities Museum at the Bibliotheca Alexandrina, who was not involved in the study, called the use of pure sand as a stabilising cushion “a brilliant, deliberate tactic”, adding that “the ancient builders profoundly understood their environment”.

The dig confirmed the scans

To test the geophysical results, the team excavated a 10-by-10-metre area within Kom C, labelled Square C1. The dig confirmed thick mudbrick walls at approximately the depths the electrical survey had predicted, providing physical evidence that the anomalies were buried architecture. The excavation also recovered a collection of artefacts: ushabti figurines, small figures placed in burials to serve the dead in the afterlife; a limestone altar with carved channels, with dried residues described as consistent with animal blood, which may indicate offerings; a faience baboon figurine, an animal associated with Thoth, god of wisdom and writing; and amulets depicting Egyptian deities including Isis, Horus, Taweret and Wadjet, along with a steatite scarab bearing the name of King Thutmose III. Taken together, the objects point to a religious or funerary character for at least part of the complex.

What the building was is still an open question

Its exact purpose remains uncertain. The researchers suggest it could have been a small or secondary temple, a religious service complex, a priestly house or a funerary structure, and further excavation will be needed to establish its precise function. Buto was largely abandoned after the Old Kingdom and remained unoccupied as a settlement for roughly 1,500 years before it was resettled in the Third Intermediate Period, and the Saite-period building is evidence of the city’s renewed activity in the seventh and sixth centuries BCE. The team now plans wider electrical resistivity surveys with larger electrode spacing to investigate deeper levels, alongside studies of ancient plants and the changing geology of the Nile Delta to reconstruct the landscape around Buto when the complex was built. Their paper also notes that, in addition to the known temple, another temple may remain buried under a thick clay layer at the site.