Good stuff! This has the makings of an interesting, and instantly recognisable map. I really like the lighting, the contrast in shadows, the real world feel, and where the theme is going. Hopefully you will give it the time it deserves.
Some constructive criticism.
For me, the two focal points of the outside are the rocks that run around the level, and the raised building at the back. Because of this, they should have as much impact as possible. At the moment, the rocks look a little too smooth. So much more would be added to the map if they had a really jagged more “rock like” appearance. I also think that by putting in another layer of rock above and behind the existing stuff in certain parts would make the skyline more interesting, and give the area a more believable look.
As for the main building, I think it would be a missed opportunity if it never had that “stand out” look to it. It already looks good, but it might need a bit more spice. It can be seen in many areas of the map, so I think it would be beneficial to make it look as interesting as you possibly can.
The ground also looks as though it runs along the one plane. I can’t see any slopes or steps in any of the images. Adding some will make the map in general, look a lot more interesting. Also might be worth adding subtle displacements to the floor, especially in the car park.
Telephone wires need to go somewhere, at the moment they only meet each other.
Not really too sure about the curb that changes from red, to white, and then back to red again.
The arched tunnel looks as though it could do with being more curved. Maybe use the arch tool to add more polys, and create the tunnel.
Level could also benefit from adding a few curved or angled corners to the buildings.
Otherwise, map shows loads of promise.