The two that I traveled to during my hitchiking days were the Hanford Facility in Washington State (where they made the plutonium for the first hydrogen bomb) and Rocky Flats in Colorado. Rocky Flats was mostly an underground facility, yet the eerie part was that about ground, not a single bird or bug could be found. The few scrubby grasses looked dry and stunted, but it was silent and dead.

Rocky Flats is now 'Decommissioned', but I'd be willing to bet that it's just as dead.

I actually worked in the salt mines in Carlsbad, New Mexico that are now an underground nuke storage facility.

I could have sworn they refined the plutonium for the Manhatten Project in Oak Ridge, TN.

For the manhatten project and the A Bomb for the Japs, the U-238 was done at Oakridge. For the fission reaction, it took the new element, plutonium, which Teller had produced for the first time in large quantity at the Hanford facility. The first H bomb was detonated at the Marshall Islands in 1952.