This is a favorite subject of mine. Each year at christmas I shoot something for a family card. A few years ago I was in Washington DC at the US Capital building and the christmas tree. I choose to shoot the tree and dome at dusk. This does a couple things, first it gives some shape to the dark part of the building, and second it gives som color to the sky. I used Tungsten WB and the sky turns royal blue. It's called the magic time of day because the light changes so quickly. Give it a try the next time you shoot a night building. I bet you will be surprised.