A dazzling civilization flourished in Sudan nearly 5,000 years ago. Why was it forgotten?

On the banks of the Nile River in eastern Sudan, the desert landscape is broken up by an unlikely sight. Towering towards the sky are a series of stone and granite pyramids, some reaching almost 100 feet high. But unlike their counterparts in Egypt, these monuments were largely written out of the history books – and remain relatively unknown to this day.