This is the man who today confessed that he imprisoned his daughter in an underground chamber for 24 years and fathered her seven children.
Elisabeth Fritzl, 42, was raped repeatedly since being lured into the dungeon built below the family home in a small Austrian town. Police said she had been "broken" by the experience.
Josef Fritzl, 73, admitted to police that all the children were his.
Three of them - Kerstin, 19, Stefan, 18, and Felix, five - were held captive with their mother in a series of windowless rooms and never saw the sunlight until they were freed on Saturday.
Incredibly, three others, Alexander, 12, Monika, 14, and Lisa, 16, were raised in the home by Fritzl and his wife. They were adopted by the couple and went to school, leading apparently normal lives.
The other child, a twin, died shortly after birth and the body burned by Fritzl in a boiler. Detectives today revealed details of the complex of rooms where Elisabeth was held since August 1984.
The three children kept prisoner with her were born there and are thought to have spent their entire lives underground.
Franz Polzer, head of the criminal investigations unit in the province of Lower Austria, said: "He has now said that he locked up his daughter for 24 years and that he alone fathered her seven children and that he locked them up in the cellar."
The case echoes that of Natascha Kampusch who was kept in a cellar by a paedophile in Vienna for eight years from the age of 10 until she escaped last year.
Police are now trying to discover how Fritzl managed to keep his daughter as a sex slave without the apparent knowledge of his 60-year-old wife Rosemarie at the three-storey house in Amstetten, 80 miles west of Vienna.
Elisabeth was this afternoon said to be suffering from a serious physical condition which was deteriorating.
Elisabeth, who was described as pale and malnourished with hair that had turned white, has told police she was held captive since shortly after her 19th birthday, having been abused by her father since the age of 11.
Detectives said she appeared "greatly disturbed" during questioning. She agreed to talk only after authorities assured her she would no longer have to have contact with her father and that her children would be protected.
Fritzl, an electrical engineer, had built a series of connected chambers, less than six feet high, behind a concealed door at the house.
The chambers had areas for sleeping, cooking and washing. Investigators said the basement labyrinth even contained a padded cell.
They refused to show pictures of rooms where the children had been born and hwere the four slept. It is believed the complex extended out beneath a plot of land at the rear of the family home.
Elisabeth Fritzl, left, as a teenager and Monika, 14, one of her daughters allowed to leave the dungeon
The only door to the complex was controlled by an electronic lock that only he knew the code for. Fritzl was arrested yesterday and the children have been taken into care.
His wife told detectives she was unaware of the imprisonment and years of sexual abuse taking place in the basement. Amazingly, the couple also rented rooms to lodgers who failed to notice that anything was amiss.
The three imprisoned children were taught to read and write by their mother with Fritzl passing clothing and food through a hatch. A tube provided ventilation.
Their extraordinary captivity only ended when Kerstin fell seriously ill and had to be taken to hospital nine days ago. Police said the 18-year-old had been "surprised" when Fritzl allowed her to go to the hospital.
It was the first time she had left the dungeon.
Doctors found a handwritten note in unconscious Kerstin's pocket. It was from her mother — begging medics to save her daughter.
Baffled by the illness, the hospital launched an appeal for missing Elisabeth to come forward and provide her medical history. Fritzl freed Elisabeth and the other two children. Kerstin remains in a coma.
Today police said that when he was arrested, he initially said "nothing" although he was now co-operating with officers.
"He led a double life for 24 years," said Mr Polzer. "The family lived upstairs. He had children with his own daughter who lived downstairs.
"He did not want to give any details to officers who investigated it."
Mr Polzer said of the underground chamber: "There are a number of rooms. Everything is very, very narrow and the victim herself, the mother of these children, told us that this was continually enlarged over the years."
Police are looking at planning records to see if Fritzl ever notified authorities about the building work.
Fritzl had fooled the authorities over the years by telling them that his " missing" daughter had mysteriously returned on three occasions - in 1993, 1994 and 1997 - to dump three children on his doorstep.
He claimed each time she had left a note saying she was unable to look after them and persuaded authorities she had left to join a cult.
Fritzl and his daughter were picked up on Saturday close to the hospital where Kerstin is being treated.
He kept Elisabeth prisoner by telling her the cellar was booby trapped to explode if she attempted to escape.
Police took the retired electrician with them to discover not just the secret opening to the underground cell, which only he knew, but to slowly,carefully gain entrance because of the fear of hidden explosives.
The small, keyless door to the dungeon, barely three feet high and two feet wide, was concealed in a workshop in part of the cellar by a shelf filled with cans of paint and other containers.
"Behind the shelf was a door made of reinforced concrete, secured electronically and running on steel rails," said local police official Heinz Lenze.
"Only the suspect ( Fritzl) knew the code."
Once inside astonished police found a labrynth of tiny rooms and tight, narrow stone-lined passageways, with uneven floors and a ceiling no higher than 5ft6ins, that was continually renovated and enlarged over the years as Fritzl's "family" grew.
The retired electrical engineer, desperate to keep his evil plan secret, dug out much of the basement with his bare hands, making regular trips to local building suppliers for materials. Foam insulation was liberally applied as an effective means of sound-proofing.
"It was a prison which he installed with skill and energy," said Mr Lenze.
The only source of light for Elisabeth and the children was a harsh striplight overhead.
Quite aside from the appalling mental damage, doctors are also concerned to discover what damage has been done to their eyesight after a prolonged period underground.
A television, video recorder and a large radio were their only contacts with the outside world - apart from the hatch through which Fritzl passed them food that was cooked on 'small hot plates' on an ancient cooker, and clothes.
Some toys, paper and glue were also found in the dungeon to provided some distraction for the young captives. Their handwork can clearly be seen in the photo of the bathroom where, in an effort to alleviate their unimaginable torment, various poignant children's drawings adorn the wall.
Mr Polzer said: "The lives of the three children in the cellar is in no way comparable with the lives of their three siblings.
"Since the day they were born they have never seen the light of day. They never had any doctor to care for them when they were sick.
"They learned to speak from their mother in isolation. They were pale, and experienced having to be nearby during the ordeal their mother was put through."
The case has prompted widespread disbelief in Austria over how such abuse could have been repeated - and why it went unnoticed for so long by the authorities.
"The entire nation must ask itself just what is fundamentally going wrong," the newspaper Der Standard said today.
Questions are being asked about how neighbours could have failed to notice what was happening.
- Shocked Austrians wake up to the full horror of their third 'girl-in-a-cellar' scandal in just two years
This man is really a monster !!!!!!!! Rape case are everywhere that can be found but who on earth would even prisoned her own daughter for 24 years !!!! That's so insane. I believe that he will get his punishment from God ...
And i really hope that Elisabeth and her children's could have back their normal lives now. Hope they can stay strong to move on ... Sincerely praying for them ....