Wow...incredible job, I can't get over the amount of detail. Was this painting inspired by Frank Herbert's books by any chance? That's what I thought of the minute I saw it, the city is exactly what I envision Arakeen would look like.
Nice and all, amazing that comes from scratch however...If this is based on Dune the book and not the series up to date, there should be no trees. Dune has no trees like that or any vegitation in that large of a quanity otherwise it looks ok. Flyers would give it a more Dune-ish feel because Arrakis City is a space port...
Your environments are always so beautiful. I especially like this one though. Something about desertscapes just really appeals to me. Plus the fact that Dune is one of my favorite novels... heh, that doesn't hurt. Love the little footsteps. That was a nice touch.
Cool landscape, the terrain looks great!
Only two comments about tiny details; I think the perspective of the foot traces is too steep compared with the FOV of the rest scene (they look like they're getting smaller gradually), and second, desert areas have a very dry environment, and the atmosprere is much more clear at long distances (I've been in Egypt). I'd make the mist a little more brown to appear as a sandstorm.