The Black Hole of Calcutta was a small prison or dungeon where British prisoners of war were held for three days on 20 June 1756. in conditions so cramped that many people died from suffocation and heat exhaustion [i] Giving rise to the phrase "like the black hole of Calcutta" to describe any dark, cramped unpleasant place. The phrase was in general use into the first half of the 20th century.

References:
[i] https://en.wikipedia.org/wiki/Black_Hole_of_Calcutta

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