How to make modular rooms in unity3d?

Question

Unity

I'm trying to find material on how and in what way it is possible to do this:
1) a room to which, over time, other rooms (modules) can be connected in real time and on which it will also be possible to perform actions.
As I see the implementation:
1)Creating a map all at once, select 1 room where the player will be and open other rooms with the fog of war.
2) Take a random room, and then when a new room is opened, a generation occurs and it is added to the previous one
.