The Dungeon of Pain was a location within the Fortress of Doom, as depicted in The Adventures of Captain Proton holoprogram. It was used to detain and torture enemies of Doctor Chaotica.
In 2375 during an incident involving photonic lifeforms, Tom Paris warned Kathryn Janeway, who was about to portray Queen Arachnia, that the holodeck safety protocols would not prevent her from being restrained or put in the Dungeon of Pain by Doctor Chaotica. (VOY: "Bride of Chaotica!")