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.

Raphael Rowe visits the short-staffed Bomana Prison in Papua New Guinea, where near-constant food shortages keep the facility on the brink of chaos.

In Belize Central Prison, the inmates are told that rehabilitation comes through God. Raphael Rowe investigates if this evangelical approach works.

Though he's no stranger to life behind bars, Raphael Rowe concedes that Costa Rica's La Reforma Prison is certainly among the most intimidating.

While spending a week inside Bogotá's fortress-like prison, Raphael Rowe must negotiate the oppressive atmosphere and deal with an ominous threat.

Raphael Rowe spends a week at a maximum security prison in Craiova, Romania, where the inmates include rapists, murderers and contract killers.

Many prisons aim to punish and demean inmates. Norway's Halden Prison -- as Raphael Rowe is about to see for himself -- does things differently.

Raphael Rowe spends a week behind bars at Tacumbu prison in Paraguay, where inmates scrounge in the trash in order to pay their own way.

Schwalmstadt, a 12th-century fortress surrounded by a moat, houses some of Germany's worst offenders, many of whom attend intense therapy sessions.

The tropical island of Mauritius is home to Melrose maximum security prison, where even the smallest infraction is met with extreme punishment.

An unnerved Rowe contends with aggressive cellmates at Maseru prison, where a high number of inmates are behind bars for rape.

At Brandvlei Correctional Centre in South Africa, nearly all the convicts belong to dangerous gangs known for lethal stabbings.

Once again, Raphael Rowe volunteers to go behind bars, this time in the Philippines at Manila City Jail, one of the world's most overcrowded prisons.

Greenland's Nuuk maximum security prison houses extremely dangerous prisoners, many of whom grew up alongside the guards now watching over them.

We don't have an overview translated in English. Help us expand our database by adding one.

We don't have an overview translated in English. Help us expand our database by adding one.

We don't have an overview translated in English. Help us expand our database by adding one.

We don't have an overview translated in English. Help us expand our database by adding one.

At Finland's Kylmäkoski prison, Raphael meets violent offenders in the general population wing and bonds with the inmates, while a newcomer is attacked.

Surrounded by many inmates who struggle with crystal meth addiction, Raphael enters the Pilsen prison and discovers that some habits are hard to break.

Raphael gets a rare look inside Bangli prison, where drug offenders are forced to join a rehabilitation program and isolation is used as punishment.

At the Rove maximum security prison, many of the inmates serve time for sexual offenses while navigating grim conditions and extremely limited resources.