The industrial section of Deep Space 9 in which Bajoran forced labourers refined uridium ore when the station was the Cardassian mining facility Terok Nor, left disused after the Occupation.
Terok Nor was built in orbit of Bajor to process ore, and the ore processing centre was the reason for its existence. Bajoran workers laboured there under Cardassian overseers in heat and danger, a history recalled in Necessary Evil and Things Past.
After the Cardassian withdrawal in 2369 the refinery falls silent and Starfleet gradually converts the space to other uses. In Civil Defense, Jake Sisko, his father and Miles O'Brien are working in one of the old processing units when they trip a forgotten Cardassian security programme designed to crush a workers' revolt.
The programme floods the unit with warnings from a recorded Gul Dukat, seals the station and finally threatens to destroy it, until the crew and the real Dukat manage to shut it down.