a jail or prison (especially one that is run in a tyrannical manner)
a fortress built in Paris in the 14th century and used as a prison in the 17th and 18th centuries; it was destroyed July 14, 1789 at the start of the French Revolution
(figurative) a course of action that is unproductive and offers no hope of improvement; "all the clues led the police into blind alleys"; "so far every road that we've been down has turned out to be a blind alley"