It's interesting how it's mostly scattered small towns in East Germany, not large cities (with the exception of the Berlin city center). For instance Altenburg, which is closest to the village I grew up, so naturally I checked that first. It's a completely unremarkable little district town today with an airfield for hobby pilots, but apparently this airfield was a Soviet military base during the Cold War:

https://www.mil-airfields.de/deutschland/flugplatz-altenburg...