Level/world subdivision?

Hello everybody!

I am new to UE4 so any help would be appreciated. I am looking into a lot of different tutorials and etc but this issue I cant seem to find anywhere.

My question is : when you make an overall game for instance a city, that would be displayed in the main level editor. But if you for example walk inside of a building and than inside of a room is it still in this same world? Or do I have to create some subdivisions of the world? Like what if I want to walk inside of a building and than I appear in the forest.

thank you!

when you do the interior of a building you have the choice to make the interior in the same scene as the exterior of the building, some games have it where when you go inside it loads a different scene that just has the interior, which can improve performance.
If you want to have it go to a completely different place when you go through a door (like Narnia) then you have to figure out a portal or something like that to transport the player.