this is the "detail" process. concentrating on adding realistic touches here and there. probably the longest and most rewarding step.
i leave the background for now, working on the middle of the image, and leaving the rest for later on.

the "background" stage. important stage : with the help of color dodge, i try to make the cavern even wider and brighter than it is, in order to separate it from the foreground building. the main idea is to give a realistic distance to the background.
before doing so, i worked on the rocks in order to remove that airbrush feeling that we could perceive on ealier steps, upper right.

finishing ground and liquids. warm tones, in order to make a link between the building and the lower water. this way, all the foreground becomes warm.

Painting process is over. the background has been flattened a bit with the use of the linear gradient tool : blue layers that i erase on the foreground.
i'm satisfied now with the difference between the two main areas.

the very last touches. duplicated the main layer in order to add the "watercolor" filter in some areas. especially in order to force some contrasts. removed the filter effect on all the light halos.

i finished the picture in approximately 7 hours. during a period of two days. a fast drawing indeed, compared to my other works.