A settlement that was buried beneath the sand for thousands of years—and eluded archaeologists for centuries—is believed to be one of the largest ancient Egyptian cities ever unearthed. The site was discovered by a stroke of good luck when archaeologists began searching for the mortuary temple of the boy pharaoh Tutankhamun (r. ca. 1336–1327 B.C.) along the west bank of the Nile in Luxor. What they found instead was a well-preserved urban settlement filled with houses, streets, and walls, some of which still stand 10 feet tall. Hieroglyphic inscriptions indicate the city was called tehn Aten, or “dazzling” Aten, and...