Schkoda

But we do know SS officer Hans Kammler probably ran a secret weapons unit for the Nazis called Schkoda Works, which you can think of as the German Skunk Works.

Schkoda was split between three locations, Brno and Pilsen in Czechoslovakia, and Wroclaw in modern-day Poland.

We don't know for sure that Schkoda works existed, but there's a ton of corroborative evidence that it probably did that Nick Cook outlines in his great book, The Hunt for Zero Point.