Servus Marc,
go her for information concerning Amberg-Schafhof - menu "Bilder":
http://www.flugplatz-amberg-schafhof.de/
Nowadays most parts of the airfield are occupied by industry and a newly-built Autobahn. Just yesterday I passed this area in bus and nothing is visible any more.
49.398155,11.974025 (Google coordinates)
"Diana" seems to be a very lonely site and until 1989 it had been behind the Iron Curtain. The aluminum material seems to have been collected after the war to be used again. The communist system seems to have prevented this whereas in the west everything went into the furnaces to be re-used.
Intersting the two-track tunnels. Better suited for production than the narrow Wertheim tunnel...
Regards
Roland