Hey Miguel, Nice drawing. I think what's happening is that it seems flat. There is no sense of depth. This is because of your edges mostly and a lack of atmospheric perspective. Remember, as things move away, they take on more of the color of the sky, and the edges get softer. Things in the foreground have sharper edges and are more saturated with color. This looks like everything is on the same focal plane. I hope this is helpful :)

Very nice study. Love the light and shadow. Maybe perspective could be improved a bit. It looks somewhat flat, which distracted me slightly, and that could be because the photo is taken from really far away with a telephoto lens. However you could cheat that a bit to angle some lines slightly toward a really far vanishing point, which would add better dimension, and make that beautiful lighting really sing without distractions.