This is the vault where you'll emerge from. There's limited loot but there's a couple notable ones.
Kitchen area has a recreation terminal where you can eject the game tape “Red Menace”. This counts towards the RobCo magazines collectibles.
Overseer room has a unique weapon called Cryolator inside the security gate and locked container. You can use a glitch to have Dogmeat fetch it for you near the start of the game.