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They call it The Tomb of the Unknowns – a vast airport hangar filled with the ghosts of 9/11.

As the tenth anniversary of September 11, 2001 draws near, the mass of mangled fire ­engines, police cars, trains and ­girders from the World Trade Center are a haunting reminder of the worst terrorist atrocity in history.

A red fire jeep – its roof peeled off like an open tomato soup can – is so badly twisted it is ­impossible to tell the front from the back.

A police cruiser sits dented, its windows smashed out and rubble embedded in the seats. Around it lingers, faint but ­unmistakable, the acrid smell that ­permeated New York for weeks after Al-Qaeda terrorists flew two planes into the Twin Towers, ­causing the deaths of 2,753 ­people.

But it’s the smallest artefacts that are most poignant, each one a reminder of a life cut short. Identity cards, ­mangled keys, wrist-watches and mobile phones have been painstakingly logged by curators. The owners will never come to claim them.

For almost a decade Hangar 17, at the edge of New York’s JFK airport, has been a heart-breaking shrine to the victims of 9/11.

Alice Greenwald, director of the 9/11 Museum and Memorial, oversees the relics and says she is most haunted by the sight of mangled bikes.

She says: “I often think about who owned them and who left them behind. Did they go into the building and never come out? Did they survive?

“Then there are the vehicles. Not just the emergency ones like fire trucks, but the ordinary everyday cars that belonged to people like you and me. And there’s a taxi cab that gets me every time I look at it.”

Preservationists started sifting through the rubble at Ground Zero two weeks after the terror attacks, as well as picking through debris that had been taken to landfill on Staten ­Island.

Over the past five years Alice and her team of ­curators have chronicled every item. Many artefacts have been moved to a last resting place. Some, like the huge steel beams, known as tridents, from the base of the towers have become part of the ­memorial to the dead.

Alice, who previously worked at the Holocaust Memorial Museum in ­Washington DC, says she was stunned by the size of relics in the hangar.

She says: “The first time I went in there it was breathtaking. It’s 80,000 square feet and it was filled with enormous pieces of steel. Every girder is stamped with a marker, so that the builders in the 60s and 70s knew where to place each piece. I am in awe of the human ­ingenuity that ­created these towers, that were then destroyed by human intervention.”

Almost half the human ­remains found have never been identified due to the fires that blazed for days after the ­attacks. But as DNA testing improves, the New York medical examiner’s office hopes that more will be matched to names of victims. And it is ­possible Hangar 17 holds traces of those who lost their lives.

Alice says: “It is conceivable that a miniscule amount of human remains could be among the ­artefacts. We just don’t know.”

For that reason the hangar is treated as near-sacred ground.

Members of the public are not allowed into the high-security hangar. But the Port Authority managers occasionally let in victims’ families. ­Spokesman Steve Coleman says it is an ­especially poignant place for New York firefighters, who lost 343 colleagues on September 11. Steve says: “Sometimes they come to collect the girders – wrapping them in American flags. We’ve had bagpipe players sending the girders on their way.

“We’ve had 1,183 requests for World Trade Center remains. The big items like trains and fire trucks are going to museums because they need to be kept in special conditions.

“But we are giving away the steel. Our only stipulations are that the girders have to go to a public memorial and the town or city has to collect the pieces themselves.”

Fireman Steven Woodstead is at the hangar to collect steel for a memorial in South Salem.

He says: “My neighbour Tatiana Ryjoe worked in the World Trade Center. This is a way of keeping her memory alive. Just being here has made the hairs on the back of my neck stick out.”

Girders have also been sent to the Imperial War Museum London and the 9/11 London Project. In the past few weeks, Alice has overseen a steady stream of other items leaving the hangar.

An ambulance, a taxi and the twisted turnstiles from the World Trade Center railway ­station have been moved to Manhattan’s ­Memorial and Museum.

And last week a fire engine, shrouded in the Stars and Stripes flag, was solemnly transported from the hangar to be lowered into the exhibition space from a crane. The vehicle’s entire crew of 11 firefighters died when the towers collapsed. Their relatives and colleagues held a vigil as it made its final journey.

A “keep back 200ft” sign that fell off the fire engine ­remains at Hangar 17, propped against a wall. On it, someone has written “Jeff we will not forget you”.

One of the most chilling finds in the hangar is a jagged 4ft by 4ft block ­resembling a meteorite, named Compression. It is ­the result of several floors of the Twin Towers melting together in the infernal heat.

Hangar 17 worker Bob ­Rovinsky says: “Compression was one of the most poignant symbols. It’s actually four floors of the World Trade Center squashed like a pancake. It’s like a box, full of concrete, pipes and bits of ­blackened paper.”

Countless other items grab the attention in the hangar. A radio antennae from the North Tower is surprisingly unscathed, yet the hulking ­cylinder it sat on looks like a giant rusting drum, with scorched wires hanging out of gaping holes.

Larger pieces of twisted girder stand near battered vehicles, chunks of steel and two train carriages melted on to tracks.

And shrouded by plastic ­curtains are three cars – a silver coupé, a blue sedan and a white family saloon – standing in ­ghostly ­silence, like mourners paying eternal tribute to the 9/11 dead.