I studied this area intensely in college. Instead of going into international law, I jumped on the technology bandwagon.
All I have to say is that we hit some **known** nuclear enrichment areas with frameworks for yielding excess plutonium but there are likely 3-to-6 locations that are hidden. The best way to asses for hidden underground lairs is with an aerial view of Iran and use the material implications from known locations and knowledge of resource deposits to hypothesize where hidden locations might exist.
For instance, this quick google search for an image, is missing a lot, in my opinion.
The questions are: where can there be a local resource of uranium, where is that resource enriched and, finally, where is there a reactor or <other nuclear tool> that yields excess plutonium? The other thing we need to know is who were AQ Khan's successors? Khan was like an Einstein. The blueprints he and others laid out for the building of nuclear weapons live on.
Where there are underground lairs, you can also bet there are other things like centrifuges and freakin' laser beams. I am just saying, we hit a few main sites but there some we dont know about.