Egyptian researchers have found a hidden 2,600-year-old structure the size of a football field after using satellites to look below the ground at Buto, one of ancient Egypt's most sacred cities, Live Science reported. The site, also called Tell el-Fara'in, is a sprawling mound in the northwestern Nile Delta that the ancient Egyptians regarded as the home of Wadjet, the cobra goddess of Lower Egypt. Archaeologists have long excavated its upper layers, from the Macedonian Ptolemaic dynasty (305 to 30 B.C.) and the Roman era (30 B.C. to A.D. 395). Deeper, older layers, including a mound called Kom C that sits below the water table in waterlogged delta clay, had stayed out of reach.
The team first used the European Space Agency's Sentinel-1 satellite, which beams microwave pulses from orbit and measures the return, to look for subtle differences in surface moisture, elevation, and reflectivity. In those radar images they spotted a large oval-shaped anomaly beneath Kom C, 420 feet long and 203 feet wide (128 by 62 meters). To learn more without digging first, they ran 15 parallel lines of electrical resistivity tomography across about 58,100 square feet (5,400 square meters), passing electrical currents through the earth to map what was below. Between the surface and 10 feet down, they found scattered Ptolemaic and Roman debris, including displaced mudbricks, pottery shards, and broken limestone, signs of later residents dismantling older structures for reuse. Between 10 and 20 feet, they found a large mudbrick structure from the 26th dynasty, or Saite period (688 to 525 B.C.), dated by the layer, the distinctive mudbricks, pottery styles, and carbon-14 tests on associated organic material. The large structure may be a tomb, a house for priests, or a religious shrine, the team wrote in a study published in March in Acta Geophysica.
Below that, at 20 to 23 feet, they unexpectedly found a thick, clean layer of sand. Nile Delta clay absorbs moisture, swells, then contracts and shifts as it dries, a slow threat to anything heavy sitting on it. The Saite builders appear to have known that. Before laying their foundations, they packed a cushion of clean sand that would have spread the building's weight, let groundwater drain, and stopped the clay from creeping, the same logic behind 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," co-author Abdelaziz Elfadaly, of Egypt's National Authority for Remote Sensing and Space Sciences, told Live Science. "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 10-by-10-foot excavation trench, about 20 to 23 feet deep, confirmed thick mudbrick walls resting on that sand. Nearby finds hinted at a sacred function: ushabti and shawabti figurines, a limestone altar whose carved channels bore dried residues consistent with animal blood, and a faience baboon figurine of the kind associated with Thoth, the god of wisdom. The verified discovery is a large Saite-era building, still mostly underground, whose survival may owe as much to a sand mattress as to the walls themselves.