The imprisonment of American Christian Pastor Saeed Abedini in Iran's infamous Evin prison has sparked an international outcry and shined a spotlight on one of the world's cruelest gulags.

But Evin is just one of many prisons where conditions exist that would shock medieval jailers, and where the level of human misery is incalculable. Prisoners brazenly carrying guns and machetes, guards rousting inmates in the night for mock executions and captives forced to stand in water up to their noses for 24 hours when they’re not being worked literally to death are common at the world's most draconian dungeons. Most operate in rogue nations, beyond the influence of human rights organizations or appeals from Western nations. The few who have escaped or been freed carry the scars from their imprisonment for the rest of their lives.

CAMP 22 and the North Korean gulag system:

Also known as Hoeryong concentration camp, and part of a large system of prison camps throughout the communist dictatorship, Camp 22 is an 87-square-mile penal colony located in the North Hamgyong province colony where most of the prisoners are people accused of criticizing the government.

Inmates, most of whom are serving life sentences, face harsh and often lethal conditions. According to the testimony of a former guard from Camp22, prisoners live in bunk houses with 100 people per room and some 30 percent bear the markings of torture and beatings -- torn ears, gouged eyes and faces covered with scars.

Prisoners are forced to stand on their toes in tanks filled with water up to their noses for 24 hours, stripped and hanged upside-down while being beaten or given the infamous "pigeon torture” -- where both hands are chained to a wall at a height of 2 feet, forcing them to crouch for hours at a time.

Tiny rations of watery corn porridge leave inmates on the brink of starvation, and many hunt rats, snakes and frogs for protein. Some even take the drastic measure of searching through animal dung for undigested seeds to eat. Beatings are handed out daily for offenses as simple as not bowing down in respect to the guards fast enough. Prisoners are used as practice targets during martial arts training. Guards routinely rape female inmates.

“The conditions are brutal,” Phil Robertson, deputy director of the Asian Division of Human Rights Watch, told FoxNews.com. “These people are constantly hungry and constantly scavenging.”

At Camp 22 and most other prisons in North Korea, getting locked up means a death sentence.

“It’s considered a one-way ticket," Robertson said. "They send you there to work you to death.”

Kang Cheol Hwan was the rare exception. Imprisoned at Camp 14 for a decade beginning at age 9, his crime was being the grandson of a man who allegedly criticized the government.

“In North Korea, if one person is condemned of betraying the Kim dynasty, then all family members until the third generation can be sent into prison,” Hwan, who is now executive director of the North Korea Strategy Center, told FoxNews.com through a translator.

Prisoners toiled 15 hours a day in mines, at lumber mills or in manufacturing, according to Hwan.

“Prisoners worked every day from 5 a.m and only had two days to rest a year," he said. "They barely had any food to eat, the food was mostly based on corn and it wasn’t sufficient. This is why most people were eating whatever they could find, including rats. At a young age I realized the benefits of breeding rats.

“I was lucky to have learned how to survive and stay strong," he added. "But I had to watch many people die out of starvation and sickness.”

La Sabaneta, Venezuela

Venezuelan President Hugo Chavez called it “the gateway to the fifth circle of hell.” At La Sabaneta prison, some 30,000 inmates live in a facility meant for 15,000. There's just one guard for every 150 prisoners, and gun-toting gangs led by "pranes" run protection rackets. Poor inmates pay them for everything from a place to sleep to protection from murder.

At the low-end of the inmate hierarchy, are los anegados, or "the unwanted ones." These prisoners have recently taken to stitching their mouths shut, taking literally the longstanding La Sabaneta code that says, “When one sews his own lips, no one can kill him.” And inmates do get killed, with shocking frequency. In 1994, 130 La Sabaneta inmates were burned or slashed to death with machetes during a gang fight. The following year, more than 200 inmates died in other incidents and another 624 were severely injured.

“It's a place where you literally have to keep your wits about you, or you could end up dead,” Kay Danes, advocate and founder of the Australian-based Foreign Prisoner Support Service said to FoxNews.com. “Violence is prevalent, even rape a common occurrence. Human dignity means very little and for foreigners, a single day can seem like a life sentence. It's a place where one mistake may be your last.”

Black Beach Prison, Equatorial Guinea:

Located along the coast in the capital city of Malabo, Black Beach Prison is known as one of the most notorious prisons in Africa and has an infamous reputation for neglecting the basic needs of inmates.

Torture and starvation are the norm at Black Beach, with many victims being denied medical care after being beaten. Food is so scarce many prisoners have died of starvation. Inmates are kept in their cells and shackled at their feet for more than 12 hours a day.

A large number of the current prison population are part of a failed coup d’état against President Teodoro Obiang Nguema in 2004. South African arms dealer and mercenary Nick du Toit, who spent five years in Black Beach, told Rapport that prisoners were tortured with electric shocks and burning cigarettes. One coup plotter suffered a fatal heart attack while being tortured, he said. In an article he penned entitled “My prison hell,” du Toit  wrote of how his handcuffs cut down to the bone and were left to rust in place. He lost more than 80 pounds before he was suddenly pardoned in 2009.

Tadmor Prison, Syria:

Rising up from the desert sands in eastern Syria, Tadmor Prison occupies a former military base. Known for some of the most horrific human rights violations in the world, with torture and summary executions occurring every day, the prison houses dangerous criminals side-by-side with political prisoners.

The most infamous episode in Tadmor's bloody history came on June 27, 1980, when all 500 inmates were shot dead by the forces of Rifa’al Assad, brother of then-President Hafez al-Assad and uncle of current President Bashar al-Assad. The ultimate penalty, dished out indiscriminately and brutally, was for a failed assassination attempt on Hafez al-Assad by the Syrian Branch of the Muslim Brotherhood.

Bara Sarraj, who spent nine years at Tadmor after being arrested in 1984 as a student in Damascus, believes the death toll was much higher than 500.

“Tadmor has no trace of life,” Sarraj told Voice of America. “There are no books, no radios, nothing. They don’t even have salt to spray over your food. Sometimes there are no needles to sew our clothes. It’s indescribable, and the constant torture, that was unique to that place. At all times, even during the night.”

Sarraj, now an immunologist at Northwestern School of Medicine in Chicago, has a chillingly lyrical name for the prison where he spent nearly a decade: “Symphony of Fear.”

The prison was shut down in 2001 but was re-opened in June 2011. Guards at Tadmor are given free reign in handling prisoners and often dole out beatings, torture, hangings, and even chop off body parts of anyone considered a traitor.

Evin House of Detention, Iran:

Nicknamed Evin University for the large amounts of academic and political prisoners held there, Evin prison is one of the world’s most brutal detention facilities.

Beatings, torture, mock executions and brutal interrogations are routine for the estimated 15,000 inmates housed in the low-slung and drab house of horrors on the outskirts of Tehran. Evin was built during the reign of Mohammad Reza Pahlavi -- known to Americans as the Shah of Iran. Before he was ousted from power in the 1979 revolution, the prison housed some of the very radicals and sympathizers who would one day rule the Islamic Republic. During the 10-year reign of Ayatollah Ruhollah Khomeini, thousands of political prisoners were systematically murdered at Evin.

“When you clear the gates, you are immediately blindfolded and brought underground,” Marina Nemat, a former inmate, told FoxNews.com in a previous article about Evin. “They take you for interrogation. They take you to a hallway and sit you down. You are there for a long time. If you move or say anything you are beaten. You must sit perfectly still, while still blindfolded, and you can wait for hours, days or even weeks.”

Nemat, who is a writing instructor at the University of Toronto, added most captors are taken to an interrogation room where the goal is anything but forcing the truth out of an inmate.

“They are not looking for information," said Nemat, now a instructor at University of Toronto and author of "Prisoner of Tehran," a 2007 book detailing her ordeal and a second memoir entitled, "After Tehran." "What they want is for you to admit that you affected the national security of Iran.”

Former inmates tell of being rousted from their cells in the night, blindfolded and taken before firing squads, only to get a last minute "reprieve," and be returned  to their cages. Closed-circuit televisions show religious propaganda and recorded confessions from the leaders of opposition groups who had broken under torture, and food is scarce.