Since the terraforming has been focused on already, I won't review. I think what's been stated is fine enough for that (maybe go over some areas a tad bit though). Also, the theme- I know that you followed the styles of sg2 and sg4. It's been discussed on this thread already so I'll leave that part alone as well :3 I'll try hitting the points that others have not yet.
Custom Trees- With custom trees (and this is just my personal opinion), I think it's best to either have them or don't have them. In this map, there's mainly default trees (about 95-97%) but there's several custom trees. I think this throws off that area a bit and makes it odd. I think custom trees are good since they show a farther level of dedication to the map but they are only good if ALL the trees are custom (again, just my opinion)
Sewer System- Sewers are way overdone... They seem to be becoming the new dragons or windmills. Teweran Survival Games 3 does have a sewer system as well but the way they did it was unique and never before done. I think if you alter the sewer system and made it unique, it would add so much depth to your map.
Train- Again, trains are a bit overdone as well but this one does happen to be different than the normal train. Even with that said, I think it could definitely be improved by quite a bit. For starters, the shape looks a little odd and at the very top, where there's stone bricks, I think that throws off the color scheme you had.
Too Many Trees- It seems as though you put trees wherever you didn't know where to put anything else. The farther you get to the edge of the glass dome, the more dense they become. It reaches a point where they become so dense that it would drastically decrease the level of gameplay. I suggest making them more sparse in some areas. Also, it'd be nice for more stuff around the edge of the map. In a lot of places around the edge, it's just walking through trees which people don't like. Maybe add more things (smaller things to fit in those spaces).
Interiors- I've looked through every floor of every building on the map and some are nice but overall, the quality of the interiors compared to the exteriors of the buildings is much lower. Going back over those and touching them up a lot would drastically improve quality of the map.
Signs- Signs with messages like "Steve was here" really kill map themes. I've noticed a few signs on the American flag that would be an instant kill for any theme you had going there. I highly suggest removing those.
Terraforming Underwater- I know I said I wouldn't really talk much about terraforming but the terraforming underwater near the boat looks really rushed and weird. Going back over that would be very nice.
Different Themed Buildings- Overall the buildings look nice from the outside but a lot of them are themed differently. Some of them use the color scheme of quartz with brick. Others use the different types of stone bricks. This gives a massive contrast between buildings that should blend together creating a theme.
Honestly, that's it for my review :3 It wasn't as long as I usually make them (probably because I'm really tired) but I think it sums everything up. Overall I give the map a 6.2/10 at the current moment.