The Compound (simply called Sewer in the PIP-Boy, and The Fishing Spot in the Fallout 4 Vault Dweller's Survival Guide) is an unmarked location in Fallout 4.
The Compound is just across the pond to the west of the village, in a sewage outtake pipe. The pipe leads out to a room where Manny confronts any outsider to the Compound. A hallway descends west past a Master-locked interrogation room toward the main part of the Compound, which is a web of catwalks.
Through an Expert-locked door to the north is a prison cell, and an office containing Dr. Roger's personal terminal. Still, the catwalks ascend higher and wind around the main room, leading to a room in the southwest corner. The hallway forks to the east and west; to the west is Dr. Rosalyn Chambers' laboratory, which contains an armor workbench and a chemistry station, as well as several locked prison cells and a terminal to unlock them; to the east is a chained door, which opens close to the interrogation room.
The Vault-Tec Corporation posters, presumably the origin of the SAFE test, originate from Vault 101.
The Compound appears only in Fallout 4.