I also went the "dark" route for this pic.
Adjusted the curves, but then took it to
Monochrome in the Channels Mixer, and lowered the blue level by -16%
I borrowed the Bird layer from Tina/Reflected Memories on Flickr, added it in Multiply at 100% opacity.
I thought that parts of the castle were still too bright, so I did some selective Burning on the castle on the Original photo.
*the blue in the upper right hand corner is on the original Bird layer (hmmmmm...that slipped by me!)