One of the reasons this photo is so brilliant is the way that the silhouetted castle almost resonate with the darkening of the sky further up. It makes for a fine balance when contrasted with the vibrant, complimentary colours of the rest of the heavens. With its fiery glow, the image is dramatic, and the hints of blue do not subtract from this, but rather adds intrigue and serves as a reminder of the mystery that lies beyond.
To me, the atmosphere speaks of the great power of nature, which you've captured fantastically. With the sturdy man-made stronghold up against it, it makes for a beautiful and significant piece. Symbolic, even.