The BBC's Laura Trevelyan visited Ground Zero, the site of the Twin Towers, ahead of the construction of a controversial memorial to the victims of the 11 September attacks was due to begin.
At the corner of the 16-acre site in Lower Manhattan where once the World Trade Center stood, a group of 20 relatives who lost their loved ones on 9/11 are standing in prayer and in protest.
Authorities say relatives were consulted over the design
The sky above is the same brilliant blue it was on that September day four and a half years ago.
Construction of the official memorial to the dead is formally beginning on Monday. Yet 1,000 relatives of those who perished have signed a petition calling for the memorial to be altered.
The winning design, called Reflecting Absence, will be based in the footprints of the twin towers, with water cascading down the sides.
A museum explaining the events of the day will be below ground.
Rosalleen Tallon, whose only sibling Sean, a fire-fighter, died on duty that day says the entire design is utterly inappropriate.
"When I remember my brother, I want to look upwards, to where the towers were, to recall how he went to heaven that day. Pushing everything underground makes me feel as though we're ashamed of the dead."
Rosalleen has vowed to sleep on the pavement at the side of Ground Zero until the Lower Manhattan Development Corporation agrees to make the changes the families are demanding.
The grief of the families is a powerful political force.
In September, after a coalition of relatives argued that plans for an International Freedom Centre (IFC) on the site could lead to views being expressed that were anti-American, the Governor of New York announced the IFC had no place at Ground Zero.
Yet of course not all family members feel the same way about what should rise from the bare rock.
Paula Berry's husband, David, was a financial analyst who died when the South Tower collapsed, leaving her to bring up three young sons alone.
Paula sat on the jury that selected architect Michael Arad's winning memorial design.
"Everyone has their own take on what the memorial should be. One has to realise there are always going to be people who aren't happy with the result," she says.
"This is so emotional, and so charged. We're all grieving, and we grieve in different ways. What people want now isn't necessarily what they want later."
Gretchen Dykstra, President of the World Trade Center Memorial Foundation, is very sympathetic to the grieving relatives. Yet her job is to get the memorial built.
She points out that the winning design was selected after an international competition, and that relatives were consulted along the way.
Ms Dykstra hopes the families will find some solace when the memorial is completed.
"I don't think I could possibly understand the pain of the relatives, of all they've gone through. But the dilemma is that their pain is infinite, whereas what we're doing is definable, it's finite," she says.
"My heart goes out to them, but that doesn't mean I necessarily agree with their perspective. However, I do not think the families should be scapegoated."
Fundraising for the $500m needed to build the memorial continues - there is a risk that adverse publicity from family members opposed to the design could put potential donors off.
But Gretchen Dykstra points out that opinion polls suggest public support for the memorial is high, something that will not be lost on donors. Fundraising is going well, she says.
Back at Ground Zero, Rosalleen Tallon is prepared to sleep on the pavement for as long as it takes. She has her brother's sleeping bag and all weather gear ready.
"I have two young children, but I am going to be here every day and every night. Because this is no way to remember the dead, how dare we say never forget but we're burying it," she tells me.
Before construction started, the only visible rebuilding work here was on the train station at Ground Zero.
There have also been differences over the Freedom Tower
But now the memorial is under way, to be completed by 2009, and next month construction is due to begin on the Freedom Tower, the 1776-foot skyscraper intended to be the landmark the Twin Towers once were.
Wrangles continue over the site - Tuesday is the deadline for the Port Authority, the owners, and Silverstein Properties, the developers, to work out their longstanding differences.
The Port Authority wants Mr Silverstein to build the Freedom Tower, but relinquish control of a major portion of the site so work can proceed simultaneously on two buildings and a nearby mall.
Mr Silverstein says he has the legal right, the will and the insurance money to do the entire project on schedule.
Governor George Pataki has ordered the two sides to agree a new lease by 14 March.
Despite all the arguing, some see grounds for hope.
"New York is a disputatious city," says Ric Bell, an architect who was consulted on the memorial design. "But I'm optimistic to see that progress is finally being made."