Here's what life is like inside Russia's toughest prison

Russian prisons are notoriously tough, but there’s one that’s even harder than the rest.

Called Black Dolphin, this high security prison on the Kazakhstan border houses the country’s most brutal criminals, including serial killers, cannibals, and terrorists, according to a documentary by National Geographic.

One prison lieutenant told National Geographic that the only way to escape is by dying.

Black Dolphin is located near the Kazakhstan border. It gets its informal name from the statue out front, made by the prisoners themselves.

Screenshot/National Geographic

The prison houses about 700 inmates, including cannibals, serial killers, and terrorists.

Screenshot/National Geographic

Combined, the inmates have killed about 3,500 people. That's an average of five murders per inmate.

Screenshot/National Geographic

Black Dolphin inmates are imprisoned for life. Vladimir Nikolayev is doing time for cannibalism.

Screenshot/National Geographic

Nikolayev killed a man during a drunken fight, then dragged him into his bathroom and chopped him up.

Screenshot/National Geographic

He ate some of the body, then gave the rest of the meat to a friend, whose wife served it to his family thinking it was kangaroo. Nikolayev is one of Russia's most notorious murderers.

Screenshot/National Geographic

Black Dolphin prisoners are kept under constant, 24-hour video surveillance.

Screenshot/National Geographic

The cells are set back behind three sets of steel doors. Inmates live in a 'cell within a cell.'

Screenshot/National Geographic

Two inmates share one 50-square-foot cell.

Screenshot/National Geographic

Guards make rounds every 15 minutes.

Screenshot/National Geographic

When inmates leave their cells, they're forced to walk bent at the waist. This technique is believed to be unique to Black Dolphin.

Screenshot/National Geographic

Inmates are blindfolded when they walk outside.

Screenshot/National Geographic

These two techniques ensure that prisoners don't have a good understanding of prison layout.

Screenshot/National Geographic

Exercise, consisting of pacing back and forth, takes place in another cell. There is no prison yard.

Screenshot/National Geographic

During exercise time, guards inspect prison cells and check for contraband.

Screenshot/National Geographic

There is no cafeteria in Black Dolphin.

Screenshot/National Geographic

Prisoners eat their meals in their cells.

Screenshot/National Geographic

Inmates are fed soup and bread.

Screenshot/National Geographic

No inmate has ever escaped from Black Dolphin.

Screenshot/National Geographic

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