Assuming no issues with delivery (I realize at this point in the war this is ASB), then Oak Ridge Tennessee and Hanford Washington.
Gotta maintain that monoploy.
Gotta maintain that monoploy.
I think they would at least demonstrate they had them; use one on a military target, be it a division, a transportation link, a battleship. Just as a bargaining chip, if they're beginning to realize they may have to think about discussing peace terms with the Allies. They were languidly pursuing nukes IOTL as it happens - they must've had some plan for them.
Or, if there was some way to convince the Allies that maybe 2 wasn't the whole inventory, and that maybe there were more available if they felt like using them. But just 2, and no more than 2? It would have been sheer suicide.
All they can realistically hope to do is delay the inevitable, but at the cost of absolutely enraging whichever country they nuke.
If you want to help the Nazi's, assuming they have a magic carpet to deliver the weapons and perfect knowledge of day to day movements, one targeting Stalin at any time during 1944 and one at the briefing of senior staff at St Paul's School in London on 15 May prior to Operation Overlord.
However, CalBear's suggestion is best - and send the second device to Carinhall assuming Fatso is home.