Even from the path below Ghûlheim, even from miles away, Bod could see that all of the angles were wrong–that the walls sloped crazily, that it was every nightmare he had ever endured made into a place, like a huge mouth of jutting teeth. It was a city that had been built just to be abandoned, in which all the fears and madnesses and revulsions of the creatures who built it were made into stone. The ghoul-folk had found it and delighted in it and called it home. (The Graveyard Book, Neil Gaiman)
This is a great description. I could attempt at a good sketch how Ghûlheim looks, and likely fail to caricaturize how Evil it looks. The wickedness of the city Neil Gaiman describes is as pointy as it needs to be: it’s a good specimen of the familiar Dark Scary Town Illustration with a touch of Tim Burton aesthetics.