I looked at this great picture (I love art deco stuff) and immediately thought of the 1920s silent film "Metropolis" that I saw in a film class waaaay back in college. A quick Google search yielded this still from the movie:http://davidszondy.com/future/city/skyscraper.htmTo my eye, the large distant structure in the Horizons backdrop very much resembles the large building in the Metropolis photo. Also, if you look closely at the old photo, there's a partially visible conical structure to the left with a dome on top that looks eerily like the row of cone things in the Horizons artwork. Very cool, to me at least.
Holy Crap! I looked at the picture again that I linked in the post above and this was in the lower left corner: http://tinyurl.com/yj3k3fkIt's freakin' exactly the same thing as the Horizons picture!
And that image, used as a book cover is originally from an edition of "Amazing Stories" (August 1939) It illustrated a story entitled "Cities of Tomorrow". The original artwork for that image was done by Julian S. Krupa. I believe it is called "The Observatory".