Although, the title of the story "Black Cat" is in some way enigmatic, I have no doubt that the setting of the events is rather realistic. I can't say that it's represented in quite a detailed way. But it's quite clear that the "darkness" and "sadness" of a background symbolize the emotional state of the main character. The thoughts of the imprisoned man who'll be executed  next morning reflects the real feelings of a person who has committed such abominable crimes but who is so eager to unburthen his soul.