Best place I ever got to go was the Pantex facility East of amarillo, TX.

It is where Nukes go to Die! They disassemble any/all Nuclear weapons down to the plutoneum core and then package the core in 3 layers of containment and store said core on site in one of their storage vaults.

I was on the first Public Media tour back in 1995 when I worked for Japanese TV.

It is an interesting place. The entire operation is in a dome structure, and is "fail safed" under 10,000 tons of gravel which is supposed to contain the radiation in the event of an accidental release during "deweaponization". Of course anyone in the facility will either be crushed by the gravel or killed by the radiation but at least the rest of us will be safe.
http://www.pantex.com/