The original photo was lacking contrast and had a bit of a magenta cast to it. My goal was to bring out more of the vivid colors of the city lights and make the mountain more visible against the late evening sky.
In Photoshop, I first ran Auto Color, then adjusted the Curves. Finally, I copied the background layer and ran Unsharp Mask with the settings of 20,50,0 and set the layer's opacity to 40%. This last technique is called "local contrast enhancement".