Could use trees and foliage (Grass decor in the terrain instance, for example). That bridge also looks like it’d be placed better in something like a city, so maybe add a few buildings.
Needs a more natural aspect. Try some other lighting settings try this Lighting Tutorial it is a bit bright so you may want to edit it a bit! Good start.
Smoothening terrain The terrain you have currently is really rough and rigid. Real-life terrain is smooth. I suggest smoothening your terrain.
Fixing sun-rays The sun is too orange, and the sun-rays are too intense. The sky is fine, but it doesn’t blend well with the awful color of the sun. I suggest changing the TimeOfDay in Lighting so that the sun has more of a peach color, and then messing with ColorShift_Top to match the sun’s color. Also, ease on the sun-rays’ intensity.
Mess with ColorCorrection/Atmosphere You’d be surprised how much you can do with ColorCorrection. I suggest you play around with it a little and see how that works for you.
Looks good so far! Some bushes, trees and some flowers would definetly help you improve the landscape. Also about the grass part. If you still want to use it, open terrain editor and use the brush tool. Select a material that is not grass, like leafy grass or mud and hold click whereever the road is grassy at. This will remove the grass on the roads, floors and etc.
Interesting, Im guessing because you have a programmer role you got it since I haven’t yet even though I replied it like a couple of hours after the post went live