Cave Entrance Speed Sketch

This depicts the process of a speed sketch. I started with a rough thumbnail done with pen on paper, then added value to the thumbnail to judge light-source and mood, and finally used the previously established scene, to create a full-color sketch.
This continues a theme I am currently exploring: Civilizations living on the water.
Ultimately, this will be turned into a full-detail matte painting; I'd like to add ruined columns into the face of the cliff to help show that the cave was man-made.
Photoshop...
Thumbnail/Value Thumbnail: 10-minutes.
Colored Sketch: 40-minutes.