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According to this Reddit page and from what I have read somewhere else Northerly Island near the Adler Planetarium is where FLW wanted it built. I can't totally confirm that. The above poster used southern Lincoln Park which looks similar to the 1950's rendering background. I've also seen people use the Buckingham Fountain site in the link. I think Northerly Island would be the best location, it's meant as a tower in the park and it's hard to shoe it in somewhere in the middle of downtown.