How to make "unexplored" areas dark

Unity Engine
1

I’m building a game that is generally normally lit. It’s structured such that the player can see into areas they aren’t currently in (over walls and such,) but I only want them to be able to see into areas they have already explored. It would be best if the areas they could see into, but haven’t explored were dark, rather than filled with fog, or some such.

Is there a way to define an area that is not lit within a scene that is lit?

Thanks!

2

One option would be to use Layers.
For example use “explored” and “notExplored” for the objects of an area. Then set the lights layer mask to “explored”, so only explored objects are lit.
If you move through the world, set all objects around the player to “explored”.