Maladomini

From Fiendish Codex II: Tyrants of the Nine Hells (3.5e):

Crumbling cities dot the decaying, pitted expanses of Maladomini. Sludge-choked rivers wend their way past endless strip mines, and sentient chunks of polluted matter crawl up onto the riverbanks, only to gasp and die upon inhaling the toxic air. Dying forests collapse, succumb to rot, or burst spontaneously into damp, smoldering flame. Like a wounded beast clinging hopelessly to life, the layer constantly shudders, moans, and weeps a foul black ichor.

From Manual of the Planes (3e):

The seventh layer of the Nine Hells is dotted with ruined, abandoned cities. Under the blood-black sky, petitioners quarry, carve, and build new cities for the Lord of the Seventh. Mine pits, slag heaps, and brackish canals cover the land like sores. Newer cities are built upon the backs of older ruins. As each city is finished, the Lord's dissatisfaction forces his subjects to begin anew.

The abandoned cities are not empty. They serve as home for petitioners who've fled their devilish tormentors, beasts from other planes who've become especially lost, and lost planar travelers who don't want to be found.