...I shall lend you a fact then.
The "Black Hole of Calcutta" was a tiny prison cell in Fort William, in the Indian city of Calcutta. According to John Zephaniah Holwell of the British East India Company, on June 20, 1756, the Nawab of Bengal imprisoned 146 British captives inside the airless room overnight — when the chamber was opened the next morning, only 23 men (including Holwell) were still alive.
...a suitable holding cell for deep staters.