The Lost Kingdom

The first thing I noticed is the rainbow. A rainbow is rarely used in landscape manipulation around here on dA (at least, that's what I think), so that's a really nice touch - it adds to the fantasy wonderland quality. The overall layout is rather neat, if you ask me. I like it. I don't think I'll be able to photomanipulate such a big landscape without it being messy. Great use of colours to make your work have a dreamy feel to it too. The perspective is considerably well done.

The depth, however, is slightly more disagreeable. The castle is unusually sharp as compared to the rest of the background. Maybe you'd like the viewers to focus on the castle, but the transition is too sharp. You can change that by either using gaussian blur on the castle a tiny bit, or find stocks with better resolution to fit with that of the castle. On the other hand, I do like the tree on the right corner, how you blurred it. However, it would be better if you made the inner portions of it darker, and the outer edges brighter. That's because the outer portions receive more light than the inner parts. [You can do that by using the alt key for the colour picker. Pick one colour on the tree itself. On a new layer on top of the tree layer, put the blend mode to multiply and, using a soft brush, start painting the shadow until it is to your liking.] - This is what I usually do to my shadows. If you have your own way, ignore this. (:

Also, maybe you'd like to edit the middle patch of trees. It stands out from the rest of the landscape. Maybe you'd like to work with the brightness and saturation a bit, make it blend more with the rest of its surroundings.

Overall, the depth is the main thing that could be edited to make the whole landscape look better. Other than that, I'd like to comment that the dreamy quality is properly conveyed. It makes a complete fantasical setting. The perspective and layout are also amazing.

I hope this critique helps you!
Cheers~