The Nucleus (formerly Mount Desert Island Naval Facility) is a pre-War submarine base owned by the United States Navy before the bombs fell. DiMA allowed the Church of the Children of Atom to utilize the place and, in return, protect his old memories from being accessed.
Mount Desert Island Naval Facility was a submarine base owned by the U.S Navy before the bombs fell. At some point before the bombs fell, the USS Democracy and her captain, Arnold Wabash, had stopped inside the base to repair the sub for redeployment. When the bombs fell, Wabash did not want to be a part of the global destruction, so he sabotaged the ship's reactor, which caused a radiation leak throughout the entire ship and base.
After some time, DiMA found the old base, and decided to stay in it. After doing all that he did, DiMA decided to leave his memories in the control room of the facility. When the Children of Atom showed up, he and Martin made a deal where the children took over the base, but had to guard DiMA's memories.
The facility exterior, made almost entirely of concrete, is built into the side of a mountain.
Continuing forward through a wooden shack, there is a wooden ramp up. If one goes up, one will arrive at the shopfront of Sister Mai, and a little bit further is the shopfront of The Archemist. Turning left and going up the stairs leads to Brother Kane and a power armor station. Going further up the stairs will lead to the entrance to the Nucleus Command Center, guarded by a zealot.
Going straight from The Archemist's shopfront, there is a staircase that goes up on the right and a staircase that goes down on the left. The staircase on the right goes through multiple wooden shacks to end up at the entrance to The Vessel. The staircase down leads to Zealot Ware. From Zealot Ware, there is another staircase on the right that leads to the bottom of The Vessel, and a ramp up. The ramp up also leads to the entrance to The Vessel.
- Brother Devin's diary - sticking out from under the mattress In Brother Devin's shack in the southwest section on the top level.
- Footlocker key - Behind the left red bench in the storage room just before the decontamination arches. Opens a footlocker in The Vessel, available during Witch Hunt.
- Taste test - To the right of Brother Kane.
- Repairs in progress - Near the decontamination arches to the east.
- Put It from Your Mind - On a chair in a shack nearest to the sub's periscope.
- High Confessor's note - Given to the player by High Confessor Tektus during Witch Hunt.
- Kiloton radium rifle sold by Brother Kane.
- Recon Marine right- and left arm - Purchased from Sister Mai / Brother Kane.
- Atom's Judgement received from Grand Zealot Richter upon completion of the quest The Heretic.
- Radical Conversion received from Sister Mai upon completion of the quest Ablutions.
- 2 fusion cores on the metal shelves in the first wooden shack upon entering.
- 2 cannonballs in a bucket up in the catwalks at the end of the first hallway to the west after exiting the end of the Nucleus Command Center, next to a huge pile of cans.
- When visiting while wearing power armor, the children may comment about how Atom powers the suit.