International Atomic Energy Agency (IAEA) General-Director Yukiya Amano looks on as he arrives for the Board of Governors meeting at the UN atomic agency headquarters in Vienna on June 4, 2013.The head of the UN atomic agency upped the ante with Iran, saying Tehran may have literally bulldozed a key part of its probe into alleged efforts to develop a nuclear bomb. Yukiya Amano of the International Atomic Energy Agency said that because of "very extensive" engineering work at the Parchin military base, visiting could now be pointless. AFP PHOTO / ALEXANDER KLEIN        (Photo credit should read ALEXANDER KLEIN/AFP via Getty Images)