Black Hole of Calcutta(noun)

a dungeon (20 feet square) in a fort in Calcutta where as many as 146 English prisoners were held overnight by Siraj-ud-daula; the next morning only 23 were still alive

Black Hole of Calcutta

a confined apartment 13 ft. square, into which 146 English prisoners were crammed by the orders of Surajah Dowia on the 19th June 1756; their sufferings were excruciating, and only 23 survived till morning.