South of Tehran, the desert gives way to barbed wire, antiaircraft guns and a maze of buildings, two of them cavernous underground halls roughly half the size of the Pentagon. International inspectors could once roam the 20 or so main buildings there, at the Natanz uranium enrichment complex. Operating more like detectives than scientists, they combined painstaking sleuthing with physics and engineering in an effort to ascertain the site’s true mission, war or peace. Full Story