City of Brass would probably work for me. As would Hestavar. I liked that article a lot.
CoB has the advantage of having a longer D&D gaming tradition, I think that would appeal to more players, and there is probably a rich story to (re)use.
I like the general idea of an epic city, but... it needs to feel epic. 20 or 30 level human city guards don't work so great for that. A 30th level bound elemental or construct hand-forged by Moradin (and given as a gift for the continued propagation of the crafts in the universe) works better, even if this creature technically fulfills the same role a human level 4 guard fulfills in Fallcrest.
An epic city needs ways to show of that this ain't [-]Kansas[/-] Nentir Vale anymore.