Federal surveillance center K-21B was a surveillance facility used by the government before the Great War. The bunker was also a contingency plan, and would serve as an outpost for government surveillance workers who were meant to continue their work well after the bombs fell. Not many workers made it to the bunker - a holotape recorded by an employee named Jeff Buzensky can be found on an employee's desk detailing the fall of the bunker and the death of his coworker Bill Stevens, who was a mere few steps away from the entrance after leaving to retrieve his personal effects from his vehicle. Unfortunately, the shelter was not stocked with enough food due to budget cuts, and its inhabitants eventually died of starvation.
On the outside of the facility, the abandoned shack has some highly irradiated water and nuclear waste barrels. The inside of the shack contains a locked trapdoor to the cellar next to Bill's skeleton and his suitcase, containing the key. The cellar leads to a large underground bunker with a large open shaft passing through the middle of the bunker. Up to three synths inhabit the bunker, one of which is a synth leader.
On the bottom floor of the bunker is a hackable terminal which can be used to reactivate the nearby elevator which leads back to the surface. However, this will also activate two hostile protectrons, which the terminal fails to disable when prompted to do so.
- Power armor frame with random leveled power armor pieces attached, on the lowest level.
- Two Vault-Tec lunchboxes: one behind the power armor frame in a small maintenance cart, and one on top of the main control center near the novice locked terminal (accessible by jumping down from the floor above).
- U.S. Covert Operations Manual #4 next to a terminal (Novice) on the lowest floor towards the northern side (on the raised part of the floor, to the left).
- Mini nuke under the stairs on the lowest floor, next to the power armor.
- Stealth Boy in the eastern corner room one floor down as one enters the surveillance center. It's located on a desk, behind a cardboard box, in the same room as the Eat'o'tronic.
- Employee 011985TP personal log holotape, on the desk near the entrance.
- Installation K-21B key and the evacuation plan note in Bill's suitcase within the abandoned shack.
- The map that is on the wall of this facility is the same map that is shown on the globe objects in the rest of the Commonwealth; this map has two errors. First, it appears to be inconsistent with the Fallout Divergence as the countries of the Soviet Union (such as Ukraine, Kazakhstan, etc) are shown to be independent. The second error is that the Black Sea, Baltic Sea and Mediterranean Sea are colored as if they were land masses and not bodies of water. The great lakes in North America are also colored in.
- There are only three actual "Radios" in the facility, on a desk in the office on the center floor. The other radio objects in the facility are named "Surveillance Device" and emit only static.
- The map marker changes from "Abandoned Shack" to "Federal Surveillance Center K-21B" after leaving the shack with the elevator.
- If the player character remains friendly with the Institute after first entering it, the synths will be allied and will not attack the player character. The synths will speak with the same dialogue as the ones found in the Institute and throughout the Commonwealth.
- Checking the database network after resetting the mainframe will show it as being online. However, all entries are deleted and text reading "For your safety, this database is now the property of the Brotherhood of Steel" can be seen.
- The interior of this location does not reset.
The abandoned shack appears only in Fallout 4.