You've got some amazing details here, but it's reading as a miniature castle in a normal sized cave to me, not as a normal sized castle in a huge cave as I think you're going for. Assuming you are going for a huge cave, I think you need to rework to rock walls.
This is a really cool idea. I cant quite put my finger on why, but I can't stop thinking that this looks like a miniature set, and not a full, life-sized city. It might be the shape of the bloom coming from the rock ceiling. Maybe its the uniformity in materials on the structures...not sure. Maybe in the shot where the…