Hey, I’ve currently got the idea of a Facility inside of a cave that manages a dam, quite a unique idea when it comes to the dam which makes it hard to get any inspiration on how to build something like it, ( Dam is inside of the Cave )
You are on a good start. I think just having the walls of the cave on the side is a good next step.
I think you should look up to how does a “dam” work.
If you’ve done you research then i have few ideas for the map.
You can make a tunnel enterence connected to a bridge that has cool view of the dam and let’s not forget that this is a “Facility” so it has to be some kind of security that checks the employees IDs etc. i hope this helps.
I do have a slight idea on how dams work, If you don’t mind sharing the ideas you have that would be great thanks!
How do you think i should go about building the walls as i did start but removed it a little while ago as it didn’t look too great
Well my bad, if you didn’t edit the post i didn’t notice/skip that the “dam” was in the cave.
What about put some big spotlights that light up the dam? It would be cool. 
You should create the cave first with terrain or what ever material or meshes then next add some greenery to make it more realistic as if it is a cave or you know its a cave (add some rocks) You could make it like an unnatural cave waterfall
I’d just add large blocks of terrain to the sides and sculpt it to look more natural.
Also, you should definitely use a real life reference image to help you.
