This is coolbert:
Here with more on the Valentin facility.
Originally built as a protected assembly point for German WW2 era Type XXI submarines, still in existence and a going concern, decades later. Very sturdily and robustly built, as they say, now having a purpose never originally envisioned!
Here the comments from two informants that HAVE ACTUALLY VISITED VALENTIN:
1. "We toured that place in 2003, film studio now!"
A FILM STUDIO!! I would have to think that in this capacity Valentin is ideally suited? Those immense thick walls make acoustics very controlled? NO outside ambient noise a distraction or problem?
And as to the very robust construction of Valentin:
2. "anything with 6 or 7 meter thick walls made of steel reinforced concrete would be next to impossible to take down without explosives, which would blow out windows in homes for miles around."
As with the German flak towers from the same era, made so robustly that demolition is either very difficult or cost prohibitive.