From A Wiki of Ice and Fire
An oubliette is a prison cell which is only accessible from above. It is impossible to escape an oubliette without help. Prisoners are often left in oubliettes to die of starvation.
According to Ser Jaime Lannister, Casterly Rock has oubliettes so small that a man cannot even sit down in one.
The Wolf's Den has oubliettes.
- ↑ A Feast for Crows, Chapter 44, Jaime VII.
- ↑ A Dance with Dragons, Chapter 29, Davos IV.