To begin to understand the pain for families who lost loved ones on 9/11, even 10 years later, Rosaleen Tallon need only read from the medical examiner's report that accompanied the return of her brother's remains:

"Sean P. Tallon . . . torso and extremities. Head absent. Reddish arm hair, multiple spine fractures, pelvic fracture, legs fractured, knees dislocated, ankles fractured and dislocated, right hand missing. Received in separate bag: head and broken helmet. Eyes not present. Decomposing."

Inside the cooling, smoking bowels of Ground Zero where Tallon-a firefighter-died when the North Tower of the World Trade Center collapsed, workers found the following possessions, and returned them also to Tallon's family: a radio, bunker pants and jacket (Sean P. Tallon written on them), Pathmark discount card, extra-large blue shirt with "Tallon" embroidered on it and the certified first responder patch on the shoulder, blue boxer shorts, blue work shorts, boots, and two white socks.

As Tallon dryly read from the medical examiner's report at a briefing last February in Washington, D.C.'s Marriott Wardman Park Hotel, dark-suited businessmen and women in the packed reception room let tears stream down their faces. In front of me a woman's shoulders heaved and she slumped forward in her chair, burying her head in her hands while Tallon spoke. I asked her later if she too had lost a loved one on 9/11, but she shook her head no. A decade on, the gruesome details of what happened to ordinary men and women at Ground Zero bereaves not only families of victims but any who revisit the day's immeasurable trauma.

Sean Tallon was 26, a Marine reservist completing his first probationary year with the New York Fire Department. He was assigned to Ladder Company 10 (the "Ten House") directly across the street from the World Trade Center's twin towers. The only son of Irish immigrants, he was living at home pending completion of his training year. His sister, now 39, describes him as "fair-haired and handsome" and "also a real wise guy" who liked to play Irish jigs on the button accordion with his dad. Sean's father, who worked directly across the river from lower Manhattan, saw the planes strike the towers, saw the flames and knew his son would head directly into the buildings, saw the buildings collapse and knew his son was crushed within.

Yet nearly half of the victims who died in the twin towers were never identified. When the city's medical examiner's office in February 2005 announced that it was closing all investigations, having exhausted efforts to identify remains despite using advanced DNA techniques, it successfully had tagged only 1,630 of the dead. Of the 2,753 who died in the World Trade Center, only 293 bodies were found intact, and only 12 could be identified by sight.

At the same time, the medical examiner's office had recovered over 21,000 body parts at the site, including 200 linked to one person. Those who knew victims discovered that the grief of losing a loved one was compounded by the heartbreak of burying only body parts, or having no one to bury at all.

That in part explains why 9/11 family organizations remain active a decade later, and why Ground Zero remains the battleground it became the day Islamic jihadists flew planes into its towers. For many family members and friends, it is the only cemetery they have to visit. "Ground Zero is sacrosanct to New Yorkers and all Americans," said Tallon, who serves as family liaison for Advocates for 9/11 Fallen Heroes. "It's hallowed by the sacrifice of those innocent victims."

Given Ground Zero's multiple layers of ownership and control, its location at the center of the world's most lucrative financial district, and its reluctant role now as a national memorial, it's perhaps no wonder that much of the last decade has been consumed in battles over how to rebuild.

The controversy that erupted in 2010 over a proposed mosque just two blocks from the 16-acre site was only the latest fight. Before that, families of the victims for years tangled with city and state authorities over an appropriate remembrance at the site, given the pressure for owners to recoup money lost from office leases there.

Leaseholder Larry Silverstein pushed for redesigned twin towers as a way to get back the 10 million square feet of office space he lost on 9/11. Architects for the new space-three skyscrapers besides the grand 1,776-foot-tall Freedom Tower-repeatedly lobbied to expand the office spaces, impinging on the grounds for the National September 11 Memorial and Museum.

Against that tide, master planner Daniel Libeskind (see "The agony of victory," March 24, 2007) designed the memorial and museum at the World Trade Center site to reach seven stories underground, encompassing the full depth of the twin towers' destruction while exposing a slurry wall that resisted the force of the attacks (but likely would have flooded the city had it cracked). Many 9/11 families, according to Tallon, objected: "Initially there would be no names of the dead at street level. We were involved in getting the names out from underground and into the light."

Another battle arose over having the names of firefighters, police, and military personnel so designated. Firefighter names are listed together but without their rank. And most recently the museum has acquired remains from the office of the medical examiner to be used as "a programmable element," Tallon said, in its exhibits. "We want these elements out of the basement and given the separate dignity that they deserve," Tallon said.

Given those skirmishes, Tallon said she thought it was "a joke" when she first heard about plans to build a mosque and Islamic community center in the old Burlington Coat Factory. The building, a squat five-story Italianate structure built in the 1800s, took severe damage on 9/11 when plane parts-including landing gears and parts of a fuselage-crashed through the roof and down through two empty floors. Most Manhattanites thought the building had emptied after that, but for months starting in 2009, hundreds of Muslims have been meeting for Friday prayer services there, listening to an imam read from the Quran.

Imam Feisal Abdul Rauf, the cleric at the center of the project along with developer Sharif El-Gamal, quietly had purchased the building in 2009. Together with a group of investors, they planned to tear down the current building and construct a 13-story Islamic cultural center and worship space. Rauf's wife, Daisy Khan, served on an advisory board for the National September 11 Memorial and Museum. One of the investors, Nour Moussa, is a nephew of the former Secretary-General of the Arab League, Amr Moussa, who is currently running for president in Egypt.

By the time Tallon and others learned of it, the Lower Manhattan Community Board already had given a go-ahead for the project. That was May 2010. Though protests over the site were growing, and there have been battles since to get the building designated a historic landmark and otherwise halt its transformation, there's little the city-or protesters-can do to stop developers who now own the site from using it as they wish.

Proponents of the project point out that there were Muslim prayer rooms inside the World Trade Center and that there are active nearby mosques predating the twin towers. Imam Rauf promised that the project will send "the opposite statement to what happened on 9/11."

But the symbolism of a high-rise Islamic center within sight of the rebuilt World Trade Center-"right on the precipice of slaughter at the hand of Islamic jihadists," as Tallon puts it-is more than many New Yorkers, or most Americans, will support.

On June 6 a crowd of 5,000 gathered near the proposed site to protest what was becoming popularly called "the Ground Zero Mosque." They included 9/11 family members as well as out-of-towners, former Muslims, community leaders and organizers Robert Spencer and Pamela Geller, who each run popular anti-jihadist blogs as well as an organization called Stop the Islamization of America (SIOA).

By July 2010 a Quinnipiac University poll showed that 52 percent of New Yorkers opposed the Islamic Center, and a CNN poll conducted late in the year showed over 70 percent of Americans nationwide oppose the project.

Struggling to recapture public-relations momentum, the developers repeatedly have changed the wording for the project, which is valued at $100 million. Initially their website referred to it as a "mosque" but later they changed that to a "prayer space" able to accommodate between 1,000 and 2,000 Muslims each Friday. Rauf named the building Cordoba House, a reference to the Great Mosque at Cordoba in Spain built to commemorate Muslim conquest of Europe. In recent weeks local New York media reported that the name had been changed to PrayerSpace.

Gamal, who remains the lead developer, has dismissed Rauf, whose ties to Hamas supporters and comments about U.S. policy serving as "an accessory to the crime" of 9/11 stirred more controversy. Gamal likes to call the project by its address, Park51.

Tallon doesn't believe Gamal would succeed with building the Islamic center were it 2002, and that the project highlights America's failure to come fully to terms with what happened at Ground Zero. "This is not about bigotry," she says, adding that her Catholic brother would have saved Muslim or Jewish victims inside the North Tower: "But my mother cannot pretend that her son was not killed by Muslims."

New York City Council member Daniel J. Halloran is one of few local politicians to support Tallon and others by opposing the Islamic community center project. Halloran, who like Tallon grew up Irish Catholic, also lost a cousin in the towers, New York firefighter Vincent Halloran.

Halloran blamed "political correctness" for the repeated decisions to move the project forward despite the objections of key 9/11 groups and of most Americans. "New York City is a melting pot, and I am tremendously thankful for the diversity, ethnically and religiously," he told me, "but they are using that as a shield to protect inappropriate planning."

A Republican with strong ties to the Libertarian Party, Halloran says there is little government can rightfully do now to stop the Islamic community center, but New Yorkers should remain wary of ongoing threats: "There are mosques in this city that supported those terrorists. And in my district, two terrorists were arrested just last week. It is still a real and present danger to the United States." Halloran also said he worries that the project represents for Islamic groups "a form of triumphalism" near the site of al-Qaeda's successful attacks.

At Ground Zero itself, the space that for 10 years has gaped open, frozen in tragedy and controversy from its yawning pit, is beginning to look ready for human life again. In what once were the footprints of the North and South Towers, fountains are flowing as water fills the giant reflecting pools ("reflecting absence" they are called to suggest the void left by the collapsing structures and the human toll). Swamp oaks are in the ground lining a plaza where family members of victims will gather on Sept. 11, 2011. From there for the first time they will be able to see the names of their loved ones engraved into a dark-bronze parapet along the outer edges of the pools.

Rising at the north end of the site is One World Trade Center, or the Freedom Tower, going up at the rate of about a new floor a week. By the 10th anniversary it should be at or above 80 floors of its 104 stories, on its way to becoming the tallest building in the United States and the most expensive (at $1,000 per square foot) in the world. (Watch live steaming video of the tower under construction.)

On the 10th anniversary of 9/11, relatives for the first time will read the names of victims from crashes at the Pentagon and Shanksville, Pa., in addition to those killed at the World Trade Center. Also a first, the names of the six victims of the 1993 World Trade Center bombing will be read-in all, 2,983 names. President Barack Obama will attend the ceremony, which also marks the opening of the National September 11th Memorial. The museum is due to be completed next year, but the memorial opens to the public on Sept. 12.

Vigilance about security is not over, and access to the ceremony will be limited to 9/11 families. Other ceremonies will be open to the public around the country, and in lower Manhattan New Yorkers plan a blocks-long hand-holding ceremony to begin on Sept. 10. Opponents of the Islamic center near Ground Zero, led by SIOA, have scheduled a protest at 2 p.m. on Sept. 11.

In addition to commemorating the 10th anniversary of the attacks, Americans will be remembering 9/11 for the first time since al-Qaeda leader Osama bin Laden was killed. Among the documents recovered in his Pakistan hideout following the May 1 raid by U.S. Navy SEALs that ended with his death, bin Laden had a hit list whose top item was a plan to celebrate the 10th anniversary of 9/11 by shooting down Air Force One with President Barack Obama aboard.

Do you worry about violence or renewed terrorism? I asked city councilman Dan Halloran. "I always worry that people will do the wrong thing, that people don't think before they act. So, yes, it's a worry. But walking up to the 10th anniversary, no one wants to talk about it."

Rosaleen Tallon and her family will commemorate 9/11 as they always do, by attending the ceremony at Ground Zero and then the Ten Firehouse where her brother worked. Her father died in 2007, but Tallon, who married just before 9/11, has three children, including a son named after her brother and one named after her father.

Despite her activism, Tallon says she won't focus on the waterfalls and the trees or the names inscribed at the memorial, things she says don't capture the destruction her family remembers. "The important thing is being where Sean's body and soul separated. And there's a spot in the sky that I look to, about in the 30s of where the North Tower stood. That has always been my imagined memorial site for him." And beyond the 10th anniversary, she said, "I will always feel it's my obligation to do anything to protect my brother's memory." That's not up to the politicians and developers, she believes: "The people have to protect the history of what happened here."