Joliet, Ill. ? When Wentworth Miller needs inspiration for his character on Fox’s “Prison Break,” he just takes a look at the fortresslike limestone walls surrounding him.

There’s nothing made-for-TV about them. Much of the adventure-drama about a man, played by Miller, trying to break his wrongfully convicted brother out of prison is filmed at the Joliet Correctional Center.

The prison, which was built mostly by convict labor in the 1850s, last held inmates in 2002. But the claustrophobic cells, steel bars, guards’ turrets, and stone floor engravings with sayings such as “It’s never too late to mend,” imbue the complex with an atmosphere the actors describe as haunting, ominous and depressing.

“The prison helps a great deal in keeping me grounded in the character,” said Miller, whose Michael Scofield character is a structural engineer with the prison’s blueprints tattooed all over his body. “When you’re surrounded by 3-foot thick walls, you really understand how impossible his task is.”

The show (8 p.m. Mondays) does require some dramatic license.

Viewers recently learned the vice president of the United States is involved in a violent conspiracy to ensure Scofield’s brother – Lincoln Burrows (Dominic Purcell) – is executed for a crime he insists he did not commit, the murder of the vice president’s brother.

Dominic Purcell plays death row inmate Lincoln Burrows on Fox's Prison

Miller’s character holds up a bank to get himself incarcerated at the fictional Fox River State Penitentiary alongside his brother, who is scheduled to be executed within months.

There, he struggles to perform his elaborate breakout plan while wrestling with the hazards of prison life – psychotic inmates, riots and this being TV, a budding romance with the prison’s comely doctor who also happens to be the governor’s daughter.

While almost all of the early shooting was done at the prison, about half of its scenes are now shot in Chicago – about 45 miles to the north – either on a soundstage or on location for non-inmate characters. The sets were built to mimic the prison’s tiny, spartan cells.

The show still relies on the former prison for shots in the infirmary, the chapel, various sheds, solitary confinement and outdoors. The yard, where much of the prisoner interaction on the show takes place, is surrounded by 12-foot fences topped with menacing barbed wire, and an old sign warns prisoners they will be shot if they approach incoming helicopters.

Producer Garry Brown said the show’s creators searched the country for a prison – and were wowed to find one that was vacant, open for shooting and featuring such beautiful-yet-forboeding Victorian architecture.

The Joliet prison is not unknown to film-location scouts – it was featured in the opening of “The Blues Brothers,” and the new feature film “Derailed,” starring Clive Owen and Jennifer Aniston, was filmed there last year.

For its starring role in “Prison Break,” little was needed to transform the site – except adding more dirt and grime.

Behind the scenes, however, changes abound.

The prison’s old shower building – where signs inform prisoners they have 15 minutes before the water is turned off – now houses the set’s snack room, with tables laden with fruit, candy, nuts and beverages.

Despite the freedom the actors have on-set, Amaury Nolasco – who plays Scofield’s cellmate – said he welcomed the chance to shed his blue prison jumpsuit at the end of the day and enjoy the comforts of home.