[Fabozz]

"It took square mile after square mile of facilities, constructed at the cost of billions, in several states."

No, you're thinking of uranium enrichment, which is a very large-scale and difficult engineering endeavor. Even then, the "square mile after square mile of facilities" was mostly required because we were trying a number of different approaches to the problem. Plutonium separation, by contrast, is an easy chemical process. All the plutonium needed by the Manhattan Project was produced in this one building at Hanford:

You can determine the scale by comparing it to the cars in the parking lot—a few hundred yards long, so bigger than one football stadium but by no means impossible to hide underground. It is completely believable that al-Tuwaitha could have a plutonium refinery in its basement.

[U S Army EOD]

Thanks for the back up, and ofcourse they also have the many acres above ground that we can see the "roofs" of the buildings and who knows (so far) what is underground.

[Erasmus]

Perhaps I should point out that

1. That building at Hanford, also referred to jocularly as the "Queen Mary," was just the tip of the iceberg. In addition, they needed the reactor buildings, water treatment plants, and so forth.

2. The Hanford reservation encompassed some 780 square miles. Of course, they were thinking expansively and, in the event conservatively, when they acquired this much land.

3. Hanford was strictly for the production of Plutonium, and was the facility that I was thinking of with regard to Plutonium when I made my original statement.