Inside the World's Toughest Prisons

Paul serves time in Piotrkow Prison, purpose-built in 2003 to contain the worst of the worst, where he meets a notorious gangland killer and learns how a zero-tolerance regime has all but wiped out the Grypser prison gang.

Paul spends time in the overcrowded and impoverished Rizal City Jail, where he shares a cell with a convicted murder and a rapist.

Crime journalist Paul Connolly is granted access to El Hongo maximum security prison, one of Mexico's toughest jails, from which no one had ever escaped.

Paul Connolly spends a week inside Danli Prison in Honduras.

Investigative journalist Raphael Rowe spends a few days -- both as a guard and a prisoner -- inside Brazil's gang-filled Porto Velho Penitentiary.

Ukraine's Zhytomyr Prison is operated with a skeleton crew that allows prisoners to freely roam the grounds -- often with potentially dangerous weapons.