Here's a picture of two cities prominent in the Blood War.
The Iron City of Dis, which makes up the entire second layer of the Nine Hells. Apart from being the home of the Lord of the Second, Dispater the Archduke, the city contains the palatial mansions of particularly important devils and officers of the Blood War. The iron walls and cobblestones of the city all glow with heat and without ironshod boots, visitors soon writhe and burn in the streets. Screaming petitioners, captives from the Blood War, and mortals kidnapped from the Material Plane fill subterranean prisons beneath the streets, their agonized cries audible from small vents in the city walls.
The Fortress of Indifference, on the 348th layer of the Abyss, is a bastion for those demons, cambions and tieflings who have turned their backs on the Blood War. Ruled by a monstrous nalfeshnee demon named Tapheon, the Fortress rises up 200 feet into the crimson Abyssal sky, on a lonely, blasted plain of tumbled rocks, jagged pinnacles and sinister gorges totally devoid of natural life. Composed mainly of black iron girdwork, humanoids both dead and undead of every variety are woven into the metal itself, used as a ghastly mortar, similar to the Wall of the Faithless surrounding Kelemvor's realm in Hades.