- "One thing I can tell you is stay the hell away from the Dunwich Building in the south, that place is bad mojo. I don't know much about it but I hear a lot of weird shit is going on."
- ―Ronald Laren
The Dunwich Building is a pre-war building located on the South-West side of the map. The location is notorious in the myth hunting community due to the common paranormal events that occur here.
Before the war, the building was owned by a company called Dunwich Borers LLC, a company that manufactured drills and other mining equipment for tunneling and drilling. In one of the rooms of the building is a Terminals. On the terminal is a transcript. On the transcript, a company employee can be heard announcing a new drill, followed by Nuclear Bombs exploding and the sound of what appears to be workers turning into Feral Ghouls. On the building, there is a door that opens by its self, although you have to be coming from the east to see it.
In the Dunwich Building Entrance, there is a self-opening door (upper area in the south corridor), however, you have to be coming from the east.
The hallucinating flashback occurs at the beginning of the Forsaken Dunwich Ruins, after a stair case and left path. In the hallucination, the player sees what the building was like pre-war. The flashbacks keep coming and going. This means that in the flashback, the player will see a man looking at a clipboard but when the flashback ends it will just be a Feral Ghoul with a clipboard on the ground beside it.
Upon entering the room where the unknown man refers to "Billy", a coffee pot is thrown to the floor and a fan is knocked over. Also, on the first floor of the building, in a room on a table is a severed head. Leaving the area through a door and returning will cause it to suddenly disappear.
The Krivbeknih is a book added in the Point Lookout DLC. It is a leather bound, blood covered book used for occult purposes. When found, the player is given a quest, The Dark Heart of Blackhall, where he has to take it to the Dunwich Building to remove its supernatural power. This is a reference to the Necronomicon of HP Lovecraft's writings, and also the cement the Dunwich Building's reputation as a paranormal hotspot. If the player drops the book on the obelisk at the bottom of the building, it will ignite in flames and also incinerate the nearby feral ghouls.
- During the flashback, the walls are still chipped and cracked, likely because the developers didn't have enough time to change it to a pre-war standard of cleanliness before releasing the game.
- The story told in the personal logs is a reference to H.P. Lovecraft's Cthulhu mythos. See especially The Dunwich Horror, the book where the name of the building came from.