Here's a look at the infamous Russian prison where US citizen Paul Whelan is being held on espionage charges

Lefortovo Prison was built in 1881 and is one of Moscow's most notorious prisons.

Joseph Stalin's NKVD agents, or Soviet secret police, tortured and killed people in Lefortovo during the Great Purge in the 1930s.

Lefortovo served as a detention facility for the KGB, the main security agency for the Soviets from 1954 to 1991. There are many rumors and legends surrounding the prison, including that a massive meat grinder was used to mash up the bodies of prisoners who were tortured to death. Legend has it that the remains were then dumped into Moscow's sewers.

Source: The Los Angeles Times

The secretive Moscow prison has long been used to house dissidents and foreign spies, both during the Soviet period and after.

Foreign spies are typically held in a single, isolated cell for their first 10 days, which is known as "quarantine" time. Their belongings are taken from them, they're dressed in blue robes, and they're not allowed to communicate with relatives.

Source: The Daily Beast

Conditions at Lefortovo are intimidating in a country that continues to face allegations of human rights abuses in its penal system, including the torture of prisoners.

Source: The New York Times

The cells in Lefortovo reportedly only have cold water and prisoners are only granted one shower a week.

Source: Novaya Gazeta

The section of the prison where foreign inmates are held is reportedly freezing and inmates don't seem to be equipped to deal with the cold.

Source: The Daily Beast

Whelan, a former Marine who worked as a global security chief for a Michigan-based auto supplies company, is reportedly being held in solitary confinement at Lefortovo.

Source: The New York Times

The Russian government has complained about the treatment of accused Russian spy Maria Butina, who is being held in solitary confinement in an Alexandria, Virginia, detention facility, and claimed the US had "tortured" her. Experts have warned the Russians will attempt to mimic the treatment of Butina in terms of their handling of Whelan.

Source: The Daily Beast; CNN

Whelan's arrest and detention comes at a time when US-Russia relations are at a historically low point. Some believe Whelan, who doesn't fit the profile of a spy, will be swapped for Butina.

Source: INSIDER

It's rare for US citizens to be arrested for espionage on Russian soil. The last time it occurred was in 2013 when US diplomat Ryan Fogle was detained and expelled by Russia over allegations of attempting to recruit a Russian intelligence officer as a spy.

The last American to be held at Lefortovo on espionage charges was Edmond Pope. A retired Navy intelligence officer, Pope was sentenced to 20 years in prison for allegedly attempting to purchase classified intelligence on Russian military technology. But Russian President Vladimir Putin pardoned Pope, who had health issues, in December 2000 and he was released from Lefortovo.