The doorway in the back of the room leads downstairs into residental room with a lot of junk items and an Ice Cooler with health items. Two more Sentry Turrets guard over a hackable terminal (Advanced) that opens up a security door with reserves of ammo and health items. After the elevator is a path that goes into a pipe to the right, while straight ahead goes deeper into the shelter. The end of a the path has an elebator that leads downward into the lower section of the shelter. You can use the terminal to deactivate the turret. There is a door with a Sentry Turret that guards over a hacable terminal (Novice) and cabinets with health items and ammo. The other two paths lead to an open area and stairway to the inner shelter.

At the threeway fork, the right section has a Stealth Boy on the ground near a dead body. Inside the shelter beyond the entrance is an underground path. There is an explosive container in this room that has grenades inside.

The Boston Mayoral Shelter sits alone on a hill and can be accessed using a terminal in the watch tower directly to the right of the shelter.

Fallout 4 fallout shelter sign