Sci-fi building

I'd say you're off to a good start. I'd say the best part here is the sky in the background. I love the wispiness of the clouds and the sunlight effects around them. The main building has a pretty interesting design, and I like the coloring. My biggest problem with it is that it doesn't really like solidly positioned on the mountain-like it's topheavy or there isn't a big enough base. I'd say you could fix that by adding something onto the lower left of the building and showing the whole building connecting more securely to the mountain. It also wouldn't hurt to make the mountain a bit flatter. The buildings on the left look better constructed, but I think you could work on the color some more. For example, make the shadowy parts as dark as you made them on the main building. You should probably make the buildings darker overall, given that they're under that cloud, but I also think the windows and other illuminated parts should be brighter. This will help with the contrast.

I like how the buildings on the right kind of fade into the distance, but I think you could add a little more detail-they look almost too vague right now. Finally, I can't exactly tell what the red and pink striped cylindrical things in the foreground are supposed to be. My guess was some sort of tube that's used in the main building, for transport or energy or something. If that's the case, then you should make them sharper looking and establish their physical connection to the building more. Finally, I'll say that your color scheme is interesting-most people think of metallic colors when they think of science fiction buildings, so it's nice to see something different.