With cardboard walls and several families sharing a single toilet, the communal Communist bedsit could only be described as a hovel.
Amid the slum conditions, gangs roamed the streets, vicious brawls were common and children died of hunger.
So it is hard to believe anyone living in such poverty could rise to become one of the world’s richest and most powerful men.
But it certainly explains Vladimir Putin’s ruthless streak.
One former friend of the child gang member turned Russian president told the Mirror: “On these streets he learnt to survive.
“It was brutal and it was mean – it was survival of the fittest. It gave him the strength to believe anything was possible.”
We found the bedsit in St Petersburg – formerly Leningrad – where Putin grew up after it was allocated to his family by the Communist Party.
His mum was 41 when she gave birth to him while still grief-stricken from the traumatic deaths of her two older sons. There were often fights inside and the area was overrun with rats.
One of young Putin’s chores was hunting and killing the rodents, but he learnt an important lesson when one bit him back.
The friend smiled and said: “I have heard him say many times since, ‘Never drive a rat to a corner.’”
Putin’s brutal early life seems to have given him a belligerence and an instinct as to when he can defy the West.
He has backed Syrian dictator Bashar al-Assad and steered Russia into conflict with neighbours such as Ukraine. Guessing the UN would fail to take action, Russian forces annexed Crimea in 2014 to bolster his strongman credentials in Moscow.
As we stand in the communal area outside his former home, a man who once knew Putin at school told us more about his life here. He recalled: “It was a very violent place and when he was young, Putin was a bad boy.
“He teamed up with one particular gang of youngsters and it was tough. This was a very, very rough area and there were many criminal gangs.
“Everyone lived in communal flats. In Putin’s there were all sorts of families from different backgrounds and there were lots of fights. You had no choice who you shared with. The walls were made from cardboard.
“Another friend of ours came back last year and said, ‘I remember how I used to beat him up. Imagine me beating up the future President of Russia?’”
The fourth-floor flat is now occupied by another family. We politely knocked on the door and asked if we could see the room where Putin grew up. “Nyet,” came the barked reply. We had outstayed our welcome and it was time to leave before the authorities were called.
Putin has apparently never returned to the place where he once lived in genuine poverty.
Now he is believed to be the world’s wealthiest man – with assets of £150billion.
He is said to control 37% of the oil company Surgutneftegaz and 4.5% of natural gas firm Gazprom. Much of the wealth is secreted away in bank accounts.
But it is most obvious in the palatial homes he has been linked with – including a Black Sea palace worth nearly £1billion. In a dossier written by a political rival, he was described as owning up to 58 planes and helicopters, 20 palaces and country retreats.
Putin’s tough-guy swagger is what drives him to amass status symbols.
He is apparently as obsessed with riches as he is with his macho photocalls – riding shirtless on horseback, hunting for Siberian tigers and posing in a tiny military submarine.
Such opulence is a far cry from his family’s humble but fascinating background. Putin’s grandfather was a chef and cooked for Stalin and Lenin.
His parents, Vladimir and Maria, married when they were both just 18.
The friend said: “His father was a sailor who served on the submarines before the war. He then went to work for the KGB. It was very dangerous work – he was a paratrooper and he went into a German occupied area to try and destroy a weapons factory.
“More than 20 soldiers went in but only three or four survived – one of them was Putin’s dad.
“But he was seriously injured and when he returned to St Petersburg he was given a menial job in a factory.
“And his mum did several jobs, mainly cleaning, just to keep food on the table and to be close to him. It was a tough life but his mum adored him.
“Her first son had died when he was a baby. The second died from starvation in the siege of Leningrad.”
Putin was born on October 7, 1952, at the local maternity hospital. We walked to the church around the corner where Putin was secretly christened. In those days religion was frowned upon in the Soviet Union and his mum took her boy when his father was at work. He attended 193 School as a junior and went on to 281 School later. His parents are both now dead.
Until his teens, Putin was part of a street gang led by a local bully. But when the ringleader was jailed, the future president decided to turn his life around by working harder at school and learning some discipline.
His old friend said: “He decided to start boxing but on his first lesson he returned home with his nose broken. His mum banned him from going but he defied her and kept going, gradually getting stronger.
“At the age of 15 he started judo and became very good. He was judo champion of Leningrad at the age of 18.”
It was during his mid-teens that Putin decided he wanted to be a spy. The friend recalled: “One of the neighbours teased him by placing a piece of used bubblegum under a park bench. He pretended it was a secret password for the KGB and Putin fell for it. He was embarrassed and was never fooled again.”
Putin learnt German and was eventually recruited by the security service.
During the Cold War he was sent to Dresden, working as a spy while using his cover as a translator.
When the Berlin Wall fell, he burned papers that could have compromised his contacts. At the age of 40 he felt his career was over and even planned to work as a taxi driver.
But he made friends with senior politicians and worked his way up the ladder. By using his rat-like cunning, he was president within a decade.
But the lessons from the streets of St Petersburg were never forgotten and still drive him to this day.