The City of the Damned is a dark and ruined city found within the Burning Hells in Act IV. It can be accessed through a passageway in the Plains of Despair. As one treks into this City, the visuals become darker and the number of demonic encounters grows steadily. Supposedly, the more evil one was in life, the deeper into Hell they will go (though it is unknown which Realm of the Great Evils it falls under). In the center of all this lies a sinister Cathedral; apparently a city hall or some other vestibule of leadership in these largely discord-ridden Plains. The stained-glass windows found within this dark cathedral are simply called "An Evil Force". Though they are destructible, they do not drop any loot. The waypoint for this location is always found close to the stairs leading down to the River of Flame, and as such the City is the geographic midpoint of the act, lying in between the Outer Steppes of the Pandemonium Fortress (separated by the Plains) and the Chaos Sanctuary (separated by the River).
"Just as the Lord of all Terror brings life to nightmares, so too can he imbue inanimate objects with his vile presence. Culled from the desecrated churches, Stained Glass Windows can sometimes be found on the Mesas in Hell. These panes of colored glass are not what they appear, however -- they are actually alive! Don't worry, adventurer, they lack both mobility and knowledge of the arcane arts and so, they cannot attack you. Perhaps, they too are used to alert the demons of the underworld of unwanted visitors... The agents of evil are everywhere in these dark days and, whether you have been aware of it or not, you are being watched!" - Deckard Cain