University of Pennsylvania Museum, Philadelphia

A remote collection of 60-foot-high dirt mounds in the southern Iraqi desert, the ruins of Nippur first attracted archaeologists’ attention in the mid-19th century. Many scholars and local citizens believed the mounds concealed a Persian castle or some rich treasure trove. When the members of the University of Pennsylvania expedition began excavating the site’s central mound in 1894, they found a 4,000-year-old ziggurat (or tiered pyramid) now known to be the base of the temple of the Sumerian storm god Enlil. (The ziggurat is visible in the center background of this photo above—taken around 1900 by the expedition’s official field photographer, John Henry Haynes, compare with modern photo of ziggurat)