This threads amazing, I clicked on it at first and looked at the first page and saw where this guy started off... and was like O_o.
then I noticed it was 9 pages long, went to the last page and saw this, hes gotten a lot better.
Very good work, keep practicing though, your skills have definitely improved though.
As for the terrain, you have some work to do with that, its rather sloppy, thats a completely different story though. Modeling geometric structures and buildings is way different from modeling terrain, it needs to be organic and flowing mostly, depending on the terrain type, and even then in real life theres hardly ever sharp edges. (except for broken rocks maybe)
Keep working though, also another way to get around people criticizing, sometimes you might be better off modeling the whole thing the way you see it in your mind, and then go about asking for criticism. Its a risk I know because people may still not like it, but sometimes you will receive unnecessary criticism when you post incomplete works, that otherwise would look fine once completed.
Keep up the good work.

I especially like the bridge, its an interesting concept, keep working on it though.