For archaeologists like Samuel Walker and his colleague Ayele Tarekegn, it’s evidence that this was once the site of a medieval city. The bits of clay are shards of pottery, the flakes of obsidian were tools used by artisans to work leather, and the stones probably were once the walls of churches and palaces.

“It’s unbelievable that it’s here,” Walker said. “When I saw this, I thought this is just the tip of the iceberg — everywhere we dig, we find stuff.”

Archaeological digs are rare in Ethiopia, despite its wealth of potential sites. “It’s a poor country, and archaeology is a very expensive subject,” said Ayele, who is trying to develop the field in the country. “It’s all to do with money and developing the expertise, the personnel and the manpower.”

Executives at DP World argue that Africa needs many more ports—especially in the Horn, where conflict has stifled trade. Ethiopia, populous and fast-growing, lost its coastline when Eritrea broke away in 1991. Its 105m people rely on Djibouti for 95% of their trade. Farther inland, countries such as South Sudan, Uganda and Rwanda struggle to reach markets. DP World thinks the region from Sudan to Somalia needs 10-12 ports. It has just half that. “The whole Horn of Africa is short of ports. It’s stifling,” says one executive.