The photograph above shows the unusual pyramids with a circle built inside them and with cross-braces connecting the circle to the corners of the pyramid. Only one pyramid is known so far built in this the way outside of Sedeinga.
At least 35 small pyramids, along with graves, have been discovered clustered closely together at a site called Sedeinga in Sudan. Discovered between 2009 and 2012, researchers are surprised at how densely the pyramids are concentrated.
In one field season alone, in 2011, the research team discovered 13 pyramids packed into roughly 5,381 square feet (500 square meters). According to archaeologists these pyramids date back around 2,000 years to a time when a kingdom named Kush flourished in Sudan.
At Sedeinga, researchers say, pyramid building continued for centuries. "The density of the pyramids is huge," said researcher Vincent Francigny, a research associate with the American Museum of Natural History in New York, in an interview with LiveScience.
Among the discoveries were several pyramids designed with an inner cupola (circular structure) connected to the pyramid corners through cross-braces. Rilly and Francigny noted in their paper that the pyramid design resembles a "French Formal Garden."
Only one pyramid, outside of Sedeinga, is known to have been constructed this way, and it's a mystery why the people of Sedeinga were fond of the design.