Fordo, revealed to the public in 2009, is Iran’s second-most-prominent nuclear enrichment facility, whose construction began in the early 2000s. Located near the city of Qom, in central Iran, it has been a source of regular controversy between Iran, Israel, the United States and other countries.

How do you blast a hole through a mountain of concrete and granite and then blow up what hides beneath it―all without crossing the nuclear line? Since the Israel-Iran conflict broke out last week, much speculation has centered on this weapon: the GBU-57/B,