Looks like you slapped a load of black on the sky of a daylight shot in Photoshop. Sorry but you really should take your shots properly and don't rely on Photoshop.

I've come back to this a few times because there is something that doesn't feel right to me. It looks, to me, as if the image of the building was placed on a black background. The edges don't seem to be exactly right. I could be entirely wrong but that's the impression I'm getting.

This looks like a day shot with the sky removed.