>>82438769
>However, the tiny chamber that is described as the oubliette, is in reality a short shaft which opens up into a larger chamber with a latrine shaft entering it from above. This suggests that the chamber is in fact a partially back-filled drain.

although some say

>An oubliette is a type of underground dungeon which was commonly used in medieval Europe.

I dont see why it wouldn't be a real thing, people were probably really bored back then, probably be quite entertaining to have a prisoner stuffed into somewhere horrible.