I need to make buildings for the side of a round cake. . . . any advise? does fondant harden?

I would use a 50/50 mix of fondant and gumpaste for structures.

Hi, I wouldn't use fondant. Gumpaste or 50/50 mixture of fondant and gumpaste works well. As it is a round cake, you need to use your tin, covered with saran wrap and let the builing cutouts dry on the side of the tin. When they are dry, they will have the curve so you can attach them easily on the round cake.

Almost duplicate post, please respond to:

http://www.cakecentral.com/cake-decorating-ftopict-663500-.html

HTH