For those of you who enjoy this kind of thing (few and far between, I'm finding) I found that the roof of the still-under-construction 龙之梦 mall at Zhongshan Park is accessible through a set of non-working escalators from the 8th floor. It gives a pretty nice view of the light rail station and former campus of Huadong University. It's being fitted with wooden "boardwalk" style floor and will probably be part of the hotel when it is finished. It's a nice bit of "urban exploring", like I said, if you're into that sort of thing. I've been up there twice, and nobody has ever said anything.