Behind Bars: The World's Toughest Prisons

Old army tents left over from the Korean War house prisoners instead of cells. Will no walls or insulation around them, prisoners endure the unbearable heat of the summer, and the freezing cold of the winter. The Sheriff is a hard man who refuses to spend any more than he has to on his prisoners. Harassment and humiliation is a part of everyday life at Tent City.

Desperate overcrowding, rats, and disease come standard in Antanimora Prison. Surrounded by the capital Antananarivo, it's bursting at the seams. It was originally built for 800 prisoners, but now it contains more than 3,000 prisoners.

A prison so fierce that guards stay outside for fear of their lives. Inside, the prisoners are in control: murderers, violent offenders, drug bosses.

The Dallas County Jail in Texas - a supersized facility with beds for 7,100 inmates. There, inmates brought in for anything from minor crime to serial killing await their court dates. Up to 300 new arrivals come in per day. The biggest threat in the prison? Turf wars. With the surplus of inmates, there is less space to divide up between them, leading to relentless gang warfare.

With a crumbling foundation more than fit for demolition, the conditions in Sofia Central prison is inhospitable for anyone, including criminals. However, with multiple prisoner cells, bunks stacked 3 stories high and horrid isolation cells, prisoners live idly behind bars for 23 hours a day.

The two toughest divisions of the Miami Dade prison complex couldn't be more different. The Miami Dade Boot Camp gives minor offenders a chance to escape the prison through rigorous and unforgiving drills and rules. To many it is a better alternative to rusty iron bars of The Miami-Dade County Jail where murderers, rapists and robbers have their own rules of survival.