Courtesy Thomas E. Levy

A honeycomb of tunnels and underground rooms runs beneath an area of Shiqmim, one of the largest Chalcolithic sites in the Negev. Before the discovery of this complex, archaeologists had believed that such structures existed only at Beer-Sheva, 12 miles to the east. To learn whether Shiqmim had such features elsewhere under its 24 acres, excavators in 1993 turned to a new technology known as geophysical diffraction tomography (GDT). See photograph of excavators using GDT microphones and GDT image.