I think I found the Wittenau Sanatorium - also known as the "Wittenauer Heilstätten" - on Google Maps.
>> Link
A bit more information:
The "Wittenauer Heilstätten" was also a part of "Aktion T4" (Action T4)...
The Nazis killed "lebensunwerte" (Life unworthy of life) people in these "Heilstätten" (a special Hospital), but of course they didn't tell the public so.
They only said that they "help" their "patients" in these "Heilstätten", but most of these "patients" were killed by the "Totenkopf-SS"; This means they are not so different from concentration camps.
I'm sorry for using some german words, but I really don't know english words for them.
+ Sorry for my sometimes terrible english .