Not that it seems to make any difference to film-makers, but Gandalf's visit to the dungeons of Dol Guldur was over and done with by the time of The Hobbit. He got the key and the map from Thrain in the dungeons, and those he turned over to Thorin early in the story. They might get around to showing the White Council attacking Dol Guldur, though. And I also shudder to think of it looking like that picture.
Minas Morgul, by the bye, was originally a fortress of Gondor, Minas Ithil, and it would make sense that it look like other places built by the Numenoreans. -- Minas Tirith, Orthanc, etc. But I don't believe they built Dol Guldur -- or is my memory just failing me?
