NEW YORK -- Just a few blocks to the north, you can still buy a latte and hail a cab, but somewhere south of Canal Street, you leave that world behind and begin your descent into the living hell that southern Manhattan has become.

The once-packed streets thin out as you pass each police barricade, the air fills with the smell of torched metal, and orange flames lick the sky.

As you approach the place that everyone is now calling Ground Zero, the colours of the city gradually disappear under a thick coat of grey ash. Ruined cars line the street, flattened and blackened apparitions. Grey smoke boils upward. Overhead, a colossal, suspended cloud of smoke covers the bottom end of Manhattan Island, casting the streets in shadow on one of the otherwise most beautiful days of the year.

The details contribute to the sense of apocalypse: Police helicopters circle like mechanical dragonflies, and F-16 combat jets scream past. At ground level, you encounter increasing devastation with each block you travel south: the wreckage of what was once the World Trade Center, the twin towers that dominated the New York skyline until Tuesday, when they collapsed after being rammed by terrorists in two hijacked airliners.

Now the buildings are an unimaginable pile of debris that fills the streets below, piled up to eight storeys deep in places, millions of tonnes of smashed concrete, twisted steel, and shattered glass and plastic, all mixed with what remains of two Boeing jetliners, countless vehicles and an undetermined number of human bodies, some so destroyed that they have, for all intents and purposes, been reduced to the molecular level.

That was the scene in southern Manhattan yesterday as North America's biggest city began dealing with the aftermath of the most devastating terrorist attack in history. At Ground Zero, the scale of the situation became all too clear as earthmovers began clawing at the wreckage.

A field morgue was set up in a building with its front ripped off.
As rescuers located bodies and body parts, they called medical teams, who catalogued and bagged them.

Although there were earlier reports that survivors were calling on cellphones from beneath the collapsed towers, no calls came yesterday. The ruins were silent.

A police officer who came away from the scene was in tears as he described the devastation, and the horror he had felt when he came upon body parts that included a head, a hand, and unidentifiable collections of muscle tissue and bone: "These were people," he said.

The hellish scene was occasionally punctuated by the eruption of flames. "We got a problem with fireballs!" came a call over a Fire Department radio. Rescue dogs clambered over the debris and workers readied a dozen 20-centimetre-high robots to search air pockets.

Only about seven storeys of the north tower remained, its girders bent outward. Late yesterday, the few remaining storeys of the south tower collapsed.

"It's horrifying," said Wilson Franco, a 25-year-old member of the Civil Air Patrol, as he delivered blankets and other supplies.

Everywhere lay the paperwork of Wall Street: charred expense reports, torn memos, ledger sheets, floppy disks. Cranes removed stones one by one from the rubble.

"I never thought I'd see the World Trade Center pass by me in a dump truck," said Craig Chester, a volunteer whose uncle was missing.

On one dusty window was a message: God Bless the Dead.

After the tragedy, New York seemed to find the kind of inner resolve that London found during the Blitz during the Second World War.

Thousands of volunteers arrived in southern Manhattan to help with the rescue effort. Among them was Stan Mattox, a 34-year-old carpenter who lost five friends in the collapse of the Trade Center.

Shortly after noon yesterday, he marched to the disaster scene with hundreds of other skilled tradesmen to help begin clearing the wreckage and hunting for bodies and survivors. Mr. Mattox, a six-and-a-half footer with the build of a weightlifter, was quietly emotional as he explained his motivation. "This thing hurts," he said. "It hurts really bad."

Frank Puccio, a 37-year-old sales manager with a cellphone company, walked through the sunlit, near-deserted streets of mid-Manhattan yesterday morning, taking in the scene and revelling in the fact that he was still alive.

"Today is different," he said. "I've always appreciated life, but now I see it for what it really is. I appreciate the sun, I appreciate the air and I appreciate being here."

It could easily have turned out far worse for Mr. Puccio, who was standing in front of the World Trade Center when the first plane hit. The impact stunned him, but he had no idea what had happened. When debris began raining from the sky, he ran into the Trade Center lobby for protection, but ran back out when police began yelling for people to leave.

Mr. Puccio called his cousin on her cellphone as he ran for safety. She met him a short distance away in her brand new BMW. Moments later, a giant chunk of flaming wreckage whistled down from the sky like an asteroid and struck the street just behind the car.

Mr. Puccio and his cousin stopped a few blocks away and watched in disbelief as the second plane hit, and as the towers collapsed into the streets below. "I've never seen anything like this in my lifetime," he said. "I don't think many people have."

For many New Yorkers, the attack and its aftermath appear to have been life altering. Charles Greene, 47, a building-maintenance worker, was standing on the curb on Avenue of the Americas when the first jet roared a few hundred metres over his head and flew into the building. Mr. Greene was philosophical as he reflected on the attack's effect on him and his city.

"It feels like it doesn't matter whether you're rich or poor today. That just isn't important. There were guys up in the World Trade Center who were billionaires. And now they're gone. I'm a poor man, but I'm still here," he said.

Indira Shockley, who lives near the World Trade Center, said she could sense that the attack would change the city forever.

"The World Trade Center is your beacon. . . . When you looked up and saw it, you could always tell where you were. Now there's just a big hole in the sky."

At the Church of Our Lady of Pompei, a midday service was held to commemorate the dead. The service was advertised with a hand-lettered sign that read: "We wrecked His world? He still loves us all. Father forgive us!"

Not everyone was magnanimous. "I know nothing's been proved," said one man. "But I feel like bombing every Muslim country on the face of the earth. Maybe it's wrong, but that's how I feel."

Powerful currents of emotion, particularly shock and grief, coursed through the city. Crowds gathered to stare at the smoke and to share their thoughts. Almost everyone had a story to tell. Some more heartbreaking than others.

In mid-afternoon, a 56-year-old bus driver named Jose Rosado stood on Avenue of the Americas at the corner of Houston Street and told how his 26-year-old daughter Maria had been trapped in an elevator when the building collapsed. Tears came to Mr. Rosado's eyes as he held up his daughter's graduation photo. She had worked as a receptionist in a contractor's office, and had recently been engaged.

A growing circle of people formed around Mr. Rosado. "Who is he?" someone asked. "His daughter got killed," someone else replied softly. A wave of sighs passed through the crowd, and several people reached out to pat Mr. Rosado's back. He was asked to hold up his daughter's photo so a television camera could capture it. Mr. Rosado did as he was asked.