Sing Sing is a maximum security prison in Ossining, New York. In the Watchmen graphic novel it is notable as the prison where Rorschach is incarcerated after being captured by New York City police, suspected of the murder of Edgar Jacobi.
In Watchmen: The End Is Nigh
Long before the Keene Act, Rorschach and Nite Owl helped to stop a massive riot in the prison. The riot turns out to be sabotage organised to help Underboss escape. However, even Underboss himself was part of a larger plan.
While incarcerated, Kovacs is interviewed and treated by Dr. Malcolm Long, a prison psychiatrist. Kovacs is also repeatedly threatened by many prisoners who have learned of his vigilante identity. While in the cafeteria line, a prisoner in line behind him, Otis, threatens Kovacs with an ice pick. However, before the hulking man can attack, Kovacs seizes a small vat of cooking fat and throws it on the prisoner, causing horrific burns. The man later dies, prompting a long time enemy, The Big Figure, to start a prison riot. However, the riot is merely a distraction, allowing Big Figure and his henchmen the opportunity to kill Kovacs in his cell. Kovacs smartly outwits Big Figure's goons and chases the diminutive gangster through the prison, finally catching him in a men's room and drowning him in a toilet.
As the riot takes place, Nite Owl and Silk Spectre both infiltrate the prison to free Rorschach. They find him just as he's closing in on Big Figure, thinking Rorschach merely needed to use the bathroom before they escape.
Sing Sing at Wikipedia