How Were the Pyramids Built? A Lost Branch of the Nile

Part of the mystery behind the construction of Egypt's ancient pyramids is that the vast majority were erected in places that now appear far from the aiding hand of the Nile river. According to new research, there's a simple explanation: We can't see what is now extinct. For some time, archaeologists have speculated that an ancient river branch ran close to 31 pyramids on the edge of Egypt's Western Desert, including the three at Giza, and likely facilitated their construction. But for the first time, researchers have mapped the entire route. They detected traces of an ancient waterway in sediment cores and radar satellite data, then drew a line to connect these sections together into "a major extinct Nile branch."

The map shows a 40-mile-long waterway dubbed Ahramat, the Arabic word for pyramids, per CNN. Researchers say it stretched a third of a mile across and was at least 82 feet deep, according to sediment cores—much like the modern Nile. It would've run almost parallel to the modern Nile, but farther west, closer to the desert and its pyramids. "The large size and extended length of the Ahramat Branch and its proximity to the 31 pyramids in the study area strongly suggests a functional waterway of great importance," says University of North Carolina Wilmington earth and ocean sciences professor Dr. Eman Ghoneim, the lead author of the study published Thursday in Communications Earth & Environment.

That "there was a waterway that could be used for the transportation of heavier blocks, equipment, people, everything, really helps us explain pyramid construction," study co-author Dr. Suzanne Onstine tells the BBC. The study notes many of the 31 pyramids, built between 4,700 and 3,700 years ago, "have causeways that lead to the branch and terminate with Valley Temples which may have acted as river harbors along it in the past." It's unclear when the river branch disappeared, but it was likely thousands of years ago. Ghoneim says it probably dried up from drought or was filled in with desertification, per CNN. According to the study, "countless" unknown temples might still be buried along the route. (More Egypt stories.)