Silver jets sparkle in the sun overhead. Skyscrapers gleam in the brilliant light, all polished glass and unbreakable steel squares.

Ferries plough white furrows across the beautiful blue of the Hudson River, the rhythmic throb of their engines propelling them towards the Statue of Liberty.

Defiantly she thrusts her torch at the streets of Manhattan where shoppers, tourists, workers and yellow cabs all jostle for elbow - and fender - room in this teeming, towering, crazy, high-rise city.

And defiantly, amid the usual cacophony of cab horns, belching bus engines and screaming police sirens, Liberty's people go about their day-to-day business even though, last night on the eve of the 9/11 anniversary, the FBI had stepped up its terror alert to orange - one below the highest level.

It said it had detected "electronic chatter" - suspicious messages on the Internet - similar to that which preceded last year's attacks, and that transport networks, power plants and banks were possible targets.

It's a beautiful New York day, just as it was a year ago when so many people made so many apparently trifling decisions - a bagel and coffee on the go and early to the desk or a leisurely breakfast with the kids - that either cost them, or saved them, their lives.

The temperature downtown is pushing 90F. Just as it was a year ago.

"I was not expecting anything so devastating," says Jim from over the water in New Jersey. "Words . . . I don't know what to say."

He's staring down into what New Yorkers now know as The Pit. It's a huge, hideous concrete cavity, the yawning remains of the 110 storeys of the Twin Towers. Each contained 96,000 tons of steel. Each was the workplace of 20,000 people. Each took only ten seconds to tumble.

How tall were they? "You just can't imagine, sonny," says an old man in a baseball cap.

He slowly lifts his arm up, over his head, over the top of the tallest tower and up through the blaze of the fierce sun until he's almost toppling over backwards. "And taller still."

They dwarfed the Deutsche Bank tower to the south, a mere 48 storeys but still neck-craningly tall. The bank is now shrouded in black gauze, like a Victorian lady swathed in mourning. No one knows what will become of it.

A few marvel at the giant message pinned to its chest - "The human spirit is not measured by the size of the act, but the size of the heart" - but most just concentrate on the size of The Pit.

In these 16 acres so many people - the rival TV networks have rival fatality counts ranging from 2,810 to 2,823 - lost their lives.

"It's not rational," says Michael, a hotel concierge from uptown. He's shaking visibly, on the point of another breakdown.

"This was my city and these were my people. I had a friend, a co-worker, a softball teammate, Kenneth Ledee, and I didn't find out until December."

Curtis, a stockbroker, who's as tall as a skyscraper, is next to him, staring down into the abyss. He had, he says, several friends who perished.

"From my office on the 40th floor over there, I could see the north tower on fire and then the second plane came screaming right over my head and . . ." He pummels his clenched right fist into his open left hand to show what happened next. It's a common gesture in New York City.

"But what I remember most was later that night, this intense rumbling noise and looking out of my apartment window on Second Avenue and these massive dump trucks rolling down here like an army. They kept rollin', rollin', rollin' for an hour."

By then, John Thomas, a firefighter from Southern California, was on the scene, part of a rescue sniffer dog team.

"The rubble was like a range of mountains ten storeys high," he says. "It was surreal. People were like ants on an anthill, but there was no organisation, they were just running around as if someone had stomped and pounded on their anthill."

He stayed for ten days, searching for as long as he could without sleep. "We found no one alive," he says sadly. Indeed, 1,721 of the bodies were never found. There was nothing left of them.

Careen, a student from Queens who's staring into The Pit, knows all the statistics although she knew no one downtown that day.

"I am human, I do have a heart," she says, unable to tear herself away from the chainlink fence around The Pit. "This was America. It represented America. Right here, this is where the whole world communicated."

But America has a problem - it doesn't know what to do next and it doesn't know what it is mourning today.

All who stare into The Pit agree it was a day that changed the world, particularly their own world, but they don't know how.

Pete, a taxi driver, is eye-poppingly, dashboard-thumpingly angry at everyone, at the whole damn f****** world.

"And if those French," he explodes, "if those f****** French ever get invaded again, don't come running to us."

Curtis, the skyscraping stockbroker, is a little more reasoned but no less belligerent.

"There's a side of everyone after 9/11 saying 'I really, really want some pain inflicted on anyone even remotely connected with pro-terrorist activities'," says this financial advisor, who weighs up million dollar deals every day.

"It's irrational because this country is founded on the premise of justice, but if you talk to anyone who you know is reasonably pacific, it's like 'sure, let's just go in there shootin'."

More immediately, America doesn't know what it is mourning today. Among the mementos festooned on the railings around St Paul's Chapel - the 18th Century "little chapel that stood" in the midst of this 21st Century nightmare - there are a few pictures and cards in memory of individual people.

There are plenty dedicated to "the heroes", a broad band of people ranging from the 343 firefighters who died, to the thousands of steelworkers who arrived, without bidding, to start clearing the wreckage.

America has spent the past year imprisoned in its own bad dreams.

"It's kinda interesting," says Curtis, the skyscraping stockbroker. "It's been a whole year where you can't focus on what happened. You wake up every morning thinking about it, but you can't focus on it, you can't comprehend it."

It's why they don't know what they're going to do with The Pit: at least the dust now billowing out of it into the Manhattan sky is no longer the dust of destruction but the dust of reconstruction.

Having removed one-and-a-half million tons of rubble, earthscrapers crawl around the hole left by the skycrapers, shoring it up and reconnecting the subways.

But once that's done, they don't know whether they're going to build on it so that future generations of brokers have a place to work, or whether they are going to "memorialise" it so that the 9/11 generation is never forgotten.

Most people don't know how they're going to mark today's anniversary. Are they going to stay at home out of respect for the dead and the ideal, or should they go to work to prove to the terrorists that nothing gets New York down?

"Hey," says the anchor on one of the 24/7 news TV channels, "if you only do one thing, just call. Just call your mom. Just call your dad. Just call someone you love. And tell them."

The most heart-rending aspect of 9/11 was the confetti of calls that fell from the silvery planes as they made their last awful arcs through the beautiful blue sky. If nothing else, this crazy, grubby, hustling, money-making city has at least learned the value of love.