Hidden under a dilapidated home in Russia is a bunker which houses an 'unregistered' prison that was abandoned several years ago.
The entrance into the facility, near St Petersburg, is covered by a concrete block, operated using a hydraulic press from the outside.
That means from the inside there is no way of unlocking the door.
Above the entrance is a sign reading “Copenhagen”.
The prison is described as something of a replica of a real detention centre in the same city, called Kresty - or formally Investigative Isolator No. 1 of the Administration of the Federal Service for the Execution of Punishments for the city of Saint Petersburg.
The underground facility reportedly copies the Kresty's cell, bed and door designs, as well as the type of locks.
It is also equipped with its own crematorium, large enough to fit one body.
Biological remains are still inside.
In one room, possibly used for torture, there are multiple electric sockets, including in the ceiling.
There is much speculation as to who operated the sinister faux prison - which closed in 2018.
It is not known for certain whether the £370,000 site had any links to Russian authorities.
It has been described as a “private mafia jail”.
The gates are decorated with a wolf, a spider, a woman behind bars, and skull and crossbones with the inscription ‘Black Hand’ – suggesting links to the Italian mafia.
It was reportedly previously owned by former Federal Penitentiary Service captain Renat Alimzanov.
He died the same year the facility appears to have closed.
Kamil Galeev, a Russian research fellow for the Woodrow Wilson Center think tank, said: "The house was probably built around 2010 but never registered. So on paper, it never existed."
Referring to the reason for existence of the underground prison, he went on to say: "Most likely explanation: Russian federal prison officer built an underground prison as an exact copy of a real prison. There he persuaded kidnapped people they are in a real prison.
"They'd give him [what] he wanted, then he'd kill and burn them."
The village has been half destroyed and the home which sits on top of the Kresty replica has been ravaged by floods.
Artur Mkrtychyan is understood to have bought the site in 2018.
Reported to be a car dealer in his 50s, he had changed his name to Artur Escobar, after Colombian drug lord and narco-terrorist Pablo Escobar.
Last year when the facility was first unearthed, a woman identified as his mother told Izvestia: “I swear I don't know anything about this.
“My hair stood on end from what you told me. It just can't be true."
Investigative journalist Sergey Kanev believes the private jail was used by a powerful mafia ring.
“We can only guess who was kept a captive there, and who was burned alive,” he said.
A similar jail was found earlier near Moscow, he said.
“There was no crematorium, but a hall of torture in the basement.
“A special iron table was installed, hostages were tied up to it and cruelly tortured.
“For example, a pool cue was used on men.
“Reluctant businessmen, debtors, thugs and hijackers of expensive foreign cars who refused to work under the right ‘roof’ were brought there.”
After reports surfaced in local media outlet 47news over the "private jail" near St Petersburg, the authorities rapidly deployed a bulldozer to bar entry.
Adding to the mystery, the Russian Investigative Committee – the main federal investigating authority in Russia - is known to have worked at the site.
The investigation is now said to be “classified”.
