I spent a lot of time thinking about how horrific an end this would be the first time I saw an oubliette. 

unknown tourist with camera photographing the grate entrance to a dungeon oubliette.

An oubliette (from the French oubliettes (noun plural)) was a form of dungeon which was accessible only from a hatch in a high ceiling.


History

To exit an oubliette was nearly impossible without outside help. The word comes from the same root as the French oublier, "to forget," as it was used for those prisoners the captors wished to forget. Most prisoners were left to die of starvation.

Known throughout Europe and even in the Middle East, these early castle prisons were usually shaped like slender cylinders. The only entrance into the windowless chambers was through a trap door in the ceiling, which opened into the floor of the guardroom above and was usually too high for the prisoners to grasp in an escape attempt. The doomed prisoners were tied to a rope and then lowered into the oubliette. They received food the same way. As indicated above, sometimes the oubliette sat below ground level. On occasion, the pit filled with water that seeped up from the earthen floor, making survival almost impossible.

The earliest known true oubliettes survive in France, at Pierrefords and at the Bastille, in Paris. The 11th/12th century Black Tower at Rumeli Hisari, in modern Turkey, contains an unusual variation. Prisoners were forced along a dark, lengthy passageway which ended above an opening in the floor through which the unsuspecting prisoners tumbled, never again to see the light of day.   Another form of oubliette was a shelf in a long steeply sloping tunnel leading down to the moat or to the sea. Once cast down the tunnel, a victim would either slowly starve or cast themselves further down to drown.  The Scots, on the other hand, fancied the bottle dungeon, a type of oubliette shaped like a bottle so that the prisoner could never lie down.

The earliest use of the word in French dates back to 1374.

At Leap Castle in Ireland workers discovered an oubliette. There are spikes at the bottom of this shaft, and when workers were cleaning it out, it took them three cartloads to carry out all the human bones at the bottom. A somewhat chilling report indicates that these workmen also found a pocketwatch dated to the 1840s amongst the bones. There are no indications of whether or not the oubliette was still in use in that period.

There is an excellent example of an oubliette at the chateau in Meung-sur-Loire near Orleans in France. This consists of a submerged structure close to the castle. There is an opening at the top which reveals a large circular stone-clad pit, approximately twenty metres in depth, approximately five metres across, with sheer walls. It has a central hole in the floor, a pit within the pit, the lower pit being used for excrement and dead prisoners.

One example of what might be popularly termed an "oubliette" is the particularly claustrophobic cell in the prison of Warwick Castle, in central England. The access hatch consists of an iron grille secured by a hasp and (now) padlock.