Ostensibly a minor quarry operated by Atomic Mining Services, the glassed cavern was actually an experimental site where AMS used atomic devices to try mine Ultracite. This also happens to be the origin of the scorchbeasts, where Enclave scientists accidentally created the monstrosities, through a combination of biological modification and exposure to radiation from Ultracite.
After the collapse of the Enclave due to infighting in 2086, following the decision to release the monsters, the Brotherhood of Steel tracked the monsters here during Operation Touchdown in 2095. Paladin Elizabeth Taggerdy gave her life trying to contain the threat and succeeded in preventing them from attacking the surface for several weeks. Her body still remains deep inside the lair, alongside equipment from the Enclave's and AMS' experiments, which according to the transmission on the last transponder next to her, left the Brotherhood in shock at discovering the scorchbeasts were man-made.
The glassed cavern is a former mining complex consisting of long underground passages. The tunnels are a long slog through hordes of Scorched. The entrance tunnel terminates in a cave-in that requires player characters to navigate through a side tunnel and two caverns containing AMS' maintenance equipment and the laboratory. This segues into the auto-miner maintenance point and a loading dock. The next stage leads to a curving cavern with a waterlogged shelter area and another small junction with a power armor frame. Along with the multiple Scorched that inhabit the mine, a scorchbeast is found near the exit elevator. Corpses of fog crawlers, cave crickets and mirelurk kings, queens, and hunters infected with the Scorched Plague litter the complex. There are also multiple scorchbeast bodies around the caverns along with the bodies of Brotherhood of Steel soldiers that killed them and wrecked auto-turrets. The complex ends with a big cavern, where the body of Paladin Taggerdy, half-buried against the eastern wall, can be found and her final moments can be heard on a transmitter. There is a mine elevator in the back of the cavern that leads topside.
- Bad news - Holotape, on the counter of one of the metal prefabricated offices, accessed by extending the walkway to it from the central structure.
- Accident - Holotape, on a bench in the locker room, end of the first stretch of the main corridor.
- I'm stuck here - Holotape, on a table inside one of the side rooms in one of the cavernous mining chambers, just before a scorchbeast carcass and the multiple dead bodies of Brotherhood of Steel members.
- Have a nice life - Holotape, on a wooden crate next to a mining helmet in one of the side mining chambers with robot charging chambers.
- Enola Walker's story, part 6 - Holotape, next to her backpack at the end of the mine, next to the elevator shaft out.
- Lieutenant Elizabeth Taggerdy's ID - Key, on Paladin Taggerdy's body in the scorchbeast chamber.
- Potential power armor chassis - A partial suit of power armor may spawn in the chamber before the scorchbeast chamber.
- Brotherhood of Steel combat armor pieces - On Paladin Taggerdy's body.
- Fusion core - In the locked storage closet in the chamber with the two concrete buildings.
- Ultracite - Ultracite ore can be found through the entire cavern, especially in the last cavern.
The glassed cavern appears only in Fallout 76.
Behind the scenes
Near the end of the cavern, close to the lift, there is a small area full of Ultracite ore and a series of wooden blocks that spell out the word "PLUGH." This is a reference to Colossal Cave Adventure, a text adventure game from the 1970s. One scenario from the game involves the player character hearing the word "plugh" coming from a hollow voice in a dark pit.