I doubt it would be free here, but I second the observation deck. Considering none of our skyscrapers have one, it would be cool to be able to do that. Also a pretty decent cash flow coming from those things if you do it right. $5-$10 just to go to the top, then there's a store with merchandise, and now you've got the attractions incorporated like the Sears Tower or John Hancock building in Chicago.
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