Behind Bars: The World's Toughest Prisons

Colony 100 – Ukraine’s prison for hardened criminals. All those behind the walls of this Soviet-built prison have either already done time.

Inmates in the Carcel Distrital in Colombia fight many battles: against other prisoners, against the guards and most of all against themselves.

The Carcel Distrital is located in one of the most dangerous quarters of Bogotá. Nearly 950 men and 50 women are imprisoned here.

El Hongo is a high-security bunker in Mexico´s desert. With sensors, cameras, mobile phone jammers, this prison is a veritable high-tech fortress.

Once, inmates in Armenian prisons fell into the hands of the "Thieves in Law," a criminal brotherhood living by its own code.

La Mesa, a Mexican prison just over the US border. The inmates? Drug traffickers, rapists, cartel killers. They have tough times ahead.