I'm afraid I will have to be a nitpicker on this one. Seems a bit soft through the whole image, and the capitol building is in shadows, no doubt from a cloud passing overhead. I'll bet a few minutes later you may have gotten the sun breaking through and hitting the capitol just right.
The appropriately lit foreground does not work with the over dark background at all. The subject also appears to be more the National Mall rather than the Capital building. It's an unfortunate effect of the situational lighting - otherwise it might have worked. It also would have helped if the Capital Building was more centered in the image rather than offset.