I was in one of the engineering units for the Graf reconstruction project in the early 80s. We built some of the tank roads and parking lots. I remember thinking it looked like a shooting range for tanks similar to a scaled up local rod and gun club range, mostly flat.
It is, primarily a tank training ground. We ‘inherited’ it from the Germans after WWII who used it for similar purposes.
A good place to train maneuver units, though the weather is usually crap (like Hoenfels)...wet and COLD!