ryuthebeardy, excellent image clean-up. This does kind of reinforce my original thought. It looks like the path/walkway is kind of arched, almost round. This wouldn't be a normal hallway, so any type of mine or cave on an island seems plausible. Two light sources might be torches. the "Amnesia" on the image tells us that it's another expansion or prequel. And the GoogleEarth locations may be zeroing in on an exact location, or further locations will follow and upcoming clues will lead us to deciding which of the locations was the right one.
Also, Dark Swarm isn't exactly a popular phrase, so the person who suggested it may be related to "Black Plague" is on to something, since the two terms are almost synonyms.