Arcassi's Necropolis
The necropolis is easy to spot, Arcassi's black tower being in the center of it, along with it being mostly made of iron it seemed like for the outer walls and some of the structures… As a high lvl lich, it was an easy task to fabricate as well as cast wall of iron to more or less make an instant town… Still, as they pegasus flew by, you could see skeleton farmers, and zombie laborers working in fields, being directed by human farmers, and generally coexistance between undead and the living.
(Anyway, we visited it as PCs, but left it sorta generic. I imagine it like Eberron's Karnath.