Pros: The 3d skybox is nice. The map itself isn't bad either.
Cons: Better skybox texture. More impressive lightning.
Improvements: Add a better skybox-texture (Use THIS tutorial to find a good one.)
Make a more impressive lightning, maybe even add a sun.
Notes: Just some ekstra things to give it the final touch:
Make HDR (Follow THIS tutorial to see how you do it)
Add some sounds, to give it atmoshpere!
In total: 7/10