Ok so I am making my Nephews Batman cake, I got a lot of inspiration here on CC, but not many people speak about how they got the effects.
So I am making a 2 tier stacked cake, coveed in yellow buttercream, I will be lining the outside of both layers in fondant buildings, now I have to admit I have not worked with fondant so my question really is, will it stand up straight if I cut building shapes out? I am afraid the buildings will begin to droop or something, also does anyone have a better suggestion then fondant for making building shapes?

I would make the buildings out of fondant with Tylose mixed in (it helps it dry harder). Cut them out & place them around the outside your cake pan so they'll have the shape of your cake. Make them well in advance, they'll need at least a day (or more) to dry. HTH

interesting, I have never heard of Tylose, how much should I put in?
I'm sure I can find it there is a really big baking supply warehouse in Manhattan. Thank you for your suggestion especialy about forming the fodant alongside the cake pan to take the shape. Great help, thank you

This gives a good explanation of how to use it. The brand I use is CK Products, but I don't really think it matters. That just happens to be the brand that my supply store carries! Good luck!
http://www.globalsugarart.com/product.php?id=17057&name=CAI%20Tylose%20Powder