The Black hole of Calcutta

The Black Hole of Calcutta was a dungeon in colonial India in which a large number of British prisoners of war allegedly died on the night of 20 June 1756. John Zephaniah Holwell, one of the survivors of the incident, was responsible for the official story.

Fort William was built by the British East India Company in 1706. In 1756, the British began to build up the fort's military defenses as a precaution against French forces in the area. Siraj Ud Daulah, the Nawab of Bengal, a hereditary local governor, ordered the British East India Company to cease their military enhancement of the fort, but he was ignored. In response, his forces laid siege to Fort William.

Nearly four days of fighting ensued, with many British casualties. The Indian forces ultimately gained the fort and took the remaining Englishmen, headed by John Holwell, as prisoners. The prisoners were initially treated well, but after some of them attacked the Nawab's guards, they were confined in a guard room and locked up overnight. This room would become the infamous Black Hole of Calcutta.

Black Hole of Calcutta was 14 by 18 feet (4.3 by 5.5 m) and had only two small barred windows. The night was hot and there was no water in the room, though the guards did provide some water when the prisoners begged for it. According to Holwell's account, some prisoners were already dead by 9:00 p.m. and the room was not opened until 6:00 the next morning. Out of 146 prisoners allegedly confined in the Black Hole of Calcutta, only 23 survived.

A 50-foot (15 m) obelisk was erected on the site of the tragedy in honor of the victims, but it was removed to the nearby St. John's cemetery in 1940, as Indian nationalists found its implications offensive.

Holwell's account may have been true or mere exaggeration. Then again, it may be that the incident was entirely a figment of his imagination.
The story of the "Black Hole of Calcutta" actually could be one of history's great scams, along with the "bombing" of the battleship Maine in Havana Harbor, the Gulf of Tonkin Incident, and Saddam Hussein's putative weapons of mass destruction.
Whatever the truth of the case, Siraj Ud Daulah, the Nawab of Bengal was killed the next year at the Battle of Plassey, and the British East India Company assumed control over most of the Indian subcontinent.