This panorama was taken from a location near the Shedd Aquarium and Adler Planetarium along the Lake Michigan coastline. The view is looking towards downtown Chicago shortly after the sun set off the left side of the photo, creating a nice glowing in the sky above the skyline. The city lights are coming on, lighting up the buildings along the shore.
More info on the original photo can also be found on the artist's website, DavidKunzman.net.