Inside the World's Toughest Prisons - Season 4

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.