So it's a post apocalyptic map? yes.
Well, I was thinking, maybe you could add in a few little hidden areas for us! Now, call me old fashioned But here are my ideas
Combine Underground base
Perhaps a Vault (Fallout 5 Confirmed)
Perhaps (I didnt look well enough) a crator for a nuke? Perhaps add some evidence of one?
And finally, perhaps a crashed airplane? ^.^