A notorious prison called 'Sailor's Silence' is being used to jail Putin critic Alexei Navalny

• Russian opposition leader Alexei Navalny was sent to a notorious prison named "Matrosskaya Tishina," or "Sailor's Silence," upon his return back to the country.
• Navalny is being held in a three-person cell for VIPs in Sailor's Silence in Moscow, according to Reuters, where political prisoners have been jailed.

Russian opposition leader Alexei Navalny was sent to a notorious prison named "Matrosskaya Tishina," or "Sailor's Silence," upon his return back to the country and as he released a bombshell look at an opulent palace he says secretly belongs to Russian leader Vladimir Putin.

Navalny, 44, returned to the country after being poisoned by a nerve agent on a flight that he alleged originated from a government-backed agent. Despite labs from several European countries confirming Navalny had been poisoned, Russia's government has denied the charge and refused to launch an criminal investigation.

After being poisoned, Navalny was transported to a hospital in Germany where he spent the next five months recovering. The outspoken Putin critic and anticorruption campaigner was sentenced to 30 days in prison and immediately detained upon arrival.

Navalny is being held in a three-person cell in Sailor's Silence in Moscow, according to Reuters, where political prisoners have been jailed.

"I'd read about it (the prison) in books and now I'm here," Navalny reportedly said on Instagram. "Russian life."

A Russian prison watchdog group said Navalny had amenities like a refrigerator, an electric kettle, a television, and hot water, according to Reuters.

But critics and watchdog groups are still raising alarms for the prison's reputation. Sergei Magnitsky, a 37-year-old tax attorney who uncovered a government corruption scheme, died in 2009 after being denied medical attention in the prison. Magnitsky was reportedly beaten by prison guards and held in inhumane conditions.

A posthumous trial by a Russian court found Magnitsky guilty of tax evasion. His name was later used for the US's Magnitsky Act in 2012 to sanction human rights offenders.

"The motto of this central Kremlin prison is isolation from information," Marina Litvinovich, a member of a prison watchdog group, told Reuters. "It's about control and isolation."

On Tuesday, an anti-corruption foundation founded by Navalny released a bombshell report alleging Putin funded a lavish $1 billion mansion through bribes. A Russian government spokesperson described the report as "pure nonsense."