Behind Bars: World's Toughest Prisons

Inside the largest Philippines women's prison: the Correctional Institution for Women. Convicts range from petty criminals to drug dealers - and the guards are outnumbered. (S3 Ep4)

Zenica prison - an 1886 fortress - is the toughest prison in Bosnia and Herzegovina. Discipline and fitness are essentials that the prison administration regularly reviews. (S3 Ep5)

Colony 8 in Ukraine is one of the toughest and most notorious prisons in the country. It is said that no one has ever escaped from here. (S3 Ep1)

A high-security prison with an area the size of ten football pitches. Surrounded by six-metre-high walls, and the sea, the facility houses up to 800 criminals. (S3 Ep2)

Urso-Branco - the White Bear - is one of the most notorious prisons in Brazil. In the past 20 years more than 100 people have died in riots. (S3 Ep3)

Inside the largest Philippines women's prison: the Correctional Institution for Women. Convicts range from petty criminals to drug dealers - and the guards are outnumbered. (S3 Ep4)

In the Philippines CIW, correction officers risk their lives to deal with more than 3000 prisoners, especially during the day, when over 1000 prisoners are not locked up. (S3 Ep6)