The shape was oddly identifiable in the blasted wreckage of the World Trade Center, standing upright amid beams bent like fork tines and jagged, pagan-seeming tridents. A grief-exhausted excavator named Frank Silecchia found it on Sept. 13, 2001, two days after the terrorist attacks. A few days later, he spoke to a Franciscan priest named Father Brian Jordan, who was blessing remains at Ground Zero.

“Father, you want to see God’s House?” he asked. “Look over there.”

Father Brian peered through the fields of shredded metal. “What am I looking for?” he asked. Silecchia replied, “Just keep looking, Father, and see what you see.”

“Oh my God,” Father Brian said. “I see it.”

As Father Brian stared, other rescue workers gathered around him. There was a long moment of silence as he beheld what he considered to be a sign. Against seeming insuperable odds, a 17-foot-long crossbeam, weighing at least two tons, was thrust at a vertical angle in the hellish wasteland. Like a cross.

Ever since the two jets had slammed into the twin towers on Sept. 11, leaving 2,753 dead, Father Brian had been asked by countless New Yorkers, “Why did God do this?” He would reply tartly, in his Brooklyn-born accent: “It had nuttin’ to do with God. This was the actions of men who abused their free will.” Now here was God explaining Himself. It was a revelation, proof that “God had not abandoned Ground Zero,” even as the awful excavations continued.

Silecchia said worriedly, “Father, they might put this in some dump heap.”

“Frankie, no,” Father Brian said. “No, they will not.”

Instead, as the 10th anniversary of the attacks nears, the “World Trade Cross” continues to occupy a central if controversial place at Ground Zero. Shortly after its discovery, Father Brian persuaded city officials to allow a crew of volunteer union laborers to lift it out of the wreckage by crane and mount it on a concrete pedestal. They placed it in a quiet part of the site, on Church Street, where on Oct. 3, 2001, Father Brian blessed it with the prayer of St. Bonaventure. “May it ever compass Thee, seek Thee, find Thee, run to Thee . . . ” When he finished, the crane operators sounded their horns, a choral blast.

Each week, Father Brian held services there. He became the chaplain of the hard hats. Whenever crews working to find the dead needed a blessing or a prayer or absolution, Father Brian would offer it. Sometimes victims’ families came to pray. The congregations grew from 25 or 35 to 200 and 300.

Men cut replicas of the cross out of ruined steel and carried them in their pockets. Even Rich Sheirer, then New York’s director of the Office of Emergency Management and a self-described “short, round Jewish guy,” appreciated the cross. “Intellectually, you knew it’s just two pieces of steel, but you saw the impact it had on so many people, and you also knew it was more than steel,” he says. Sheirer has a picture of it standing in the wreckage, as well as a small steel cutout given to him for a keepsake by the September 11th Families’ Association.

Father Brian says: “We had Jews, Muslims, Buddhists. People who believed or didn’t believe. It was a matter of human solidarity. Whether you believed was irrelevant. We needed some type of fellowship down there, other than working.”

* * *

On the same September day that a laborer stared at a T-beam and saw a cross, a traumatized architect named Michael Arad had a different sort of vision, though no less spiritual.

Arad was shaving when the first plane hit on Sept. 11. He climbed to the roof of his Greenwich Village building in time to see the second plane, United Airlines Flight 175, bank and accelerate into the South Tower, not far from where his wife, Melanie, was working. She survived, but for the next two nights Arad had terrible insomnia.

About 2 a.m. on the third night, he rose, mounted his bicycle and rode in a restless circle around Lower Manhattan. Eventually, he coasted into Washington Square Park. There, he found about a dozen other mourning insomniacs huddling by candlelight at the fountain. They stood together wordlessly, candles reflecting in the water’s smooth, black surface.

“People just had to stand next to one another at that hour, physically and emotionally,” Arad says. “I walked up to that fountain, and it just changed completely how I felt about what I had witnessed. The sense of dread and despair didn’t evaporate to nothingness, but there was this sense of hope and compassion that came in, and all of a sudden I wasn’t facing it alone.”

The impressions of that night, of dark water, grief and conciliation, stayed with him. He sketched an image of water flowing into voids that never fill. At first, “It wasn’t anything solid. It didn’t make sense,” he says. But it evolved into a design for a memorial that bespoke “a sort of persistent sense of absence, the absence of the towers not in the sky,” he says.

He called it “Reflecting Absence.” When the Ground Zero developers launched an international contest to design a monument to 9/11, he entered.

“I just wanted to know if it was something that could be made, that could be realized,” he says.

* * *

A decade later, the secular and nonsecular visions of the excavator and the architect have come together at the National September 11 Memorial and Museum, which will be dedicated Sunday, the 10th anniversary of the attacks. The journey from wreckage to remembrance has been fraught, with quarrels between developers and victims’ families over the appropriate degree of reverence on the 16-acre site.

The compromise they reached — with the help of 13 cranes and some political muscle — is a hybrid plaza with eight acres devoted to Arad’s contemplative fountains and a museum, and the other half to commercial towers. But what does and doesn’t belong there is still disputed. Particularly contentious is Father Brian’s salvaged cross, which this summer was installed in the still-unfinished museum section.

In July, the nonprofit group American Atheists sued to remove it, calling it an unlawful and “repugnant” attempt to promote religion on public land. One group member told ABC News that it was “an ugly piece of wreckage” that connoted only “horror and death.”

To which Father Brian sighs heavily. There were T-beams on every floor of the World Trade center buildings. If we are to remove from public life every object resembling a cross, he says, we have our work cut out. We can start, he suggests, “with telephone poles.”

Like it or not, to most Americans the steel and debris of the World Trade Center has become more than just wreckage. It has been alchemized into relics, not just by fire but by memory and trauma. Larger spiritual meanings have been imputed to it because of whom or what it touched.

“None of these objects are in and of themselves the reason why they’re here,” says Joe Daniels, the memorial foundation’s president. “They all represent a platform for the stories behind them. The cross is a perfect example. That was an artifact that was literally born from the site, and it played an actual role during that hellish recovery period.”

Everything at the site is hallowed, to a certain extent, to those who personally experienced Ground Zero. Like Daniels. On Sept. 11, he was another financial analyst on his way to work. He stepped off the train at 2 World Trade to what seemed like “rush hour in reverse,” crowds fleeing from a scene surreal and searing. The gaping hole in the North Tower with plumes of fire. Paper falling, intermingled with bodies. A strange dead silence for half a second when the second plane hit. Then a horrible rumble, followed by a wail.

The plane Daniels watched strike the South Tower likely destroyed the life of David S. Berry, 43, research director for the brokerage firm Keefe, Bruyette & Woods, who was on the 89th floor. Paula Berry was widowed with three young sons. She quit her publishing job to focus on raising them, and for the past 10 years the only work she has done outside her home has been devoted to the memorial. She served on the jury that chose Arad’s design and also on the Families Advisory Council. She has become a self-described “emotional gauge” for what belongs at the site, and her support for the cross was therefore crucial.

“We were all very interested in a design that treated the acres as sacred,” she says. But she emphasizes that the cross is not displayed as a religious icon. “It became obvious that it would be remiss of us not to put it in there. If you played it the other way, that would feel peculiar. Where would it go?”

The steel that fell from the sky, memorial caretakers say, has multiple meanings. At its most basic, it is evidence of a crime. Yet it is also a manifestation of the victims. “This was steel holding up the lives of people,” says Bill Baroni, deputy executive director of the Port Authority.

The Latin term for relic — reliquiae — means “remains” or “something left behind.” Somehow among 1.8 million tons of debris, salvagers retrieved some of David Berry’s things. Paula declines to say what they were. “They are things that were returned to me, and this is where I stop,” she said.

Their return, of course, can’t restore the person, any more than the memorial’s completion can unmake the event. “Do you feel less cheated?” she asks. “No. David wasn’t supposed to die.”

But what it can do, she says, is serve as a reminder that while there were twin acts of evil in New York that day, there were also hundreds of thousands of acts of good. Acts such as those performed by recovery workers, who combed so caringly through the wreckage that they were able to find something of David Berry’s. “This is really humanity at its best,” Berry says. “And to participate in this maybe softens humanity at its worst. Which is something else I experienced. That’s the best way to describe it.”

* * *

For the past decade, much of the sacred steel recovered from Ground Zero has been held in Hangar 17 at John F. Kennedy Airport.

From the outside, it’s a colorless industrial building. On the interior, it’s an unsettling sculpture garden of huge rust-colored beams bent into fantastical shapes, resembling works by Alexander Calder.

“It’s like art, right?” says Nancy Johnson, gently.

Johnson directs the World Trade Center Artifacts project and has overseen the preservation of the Ground Zero wreckage since 2006. Ten years ago, she just missed being in the North Tower in her Port Authority office on the 63rd floor because she was late to work. The steel has categories, she explains. There is composite steel, facade steel and, worst of all, “impact steel,” the melted ore struck directly by the planes. The steel at the base of the buildings was up to four inches thick. At the top, it was as thin as a quarter-inch.

Then there is that interesting category she calls “symbol steel,” the icons created by welders during their downtime. Cutouts of the skyline. Stars of David. Police shields. And, of course, crosses.

The hangar is relatively empty now compared with the tonnage it once held. Much of the steel has been scattered by the Port Authority’s 9/11 Steel Distribution Program, through which thousands of artifacts have gone to smaller memorials.

Each piece is treated reverently, escorted to its new location by police or fire units in full dress. There is now World Trade Center steel in 1,500 parks and fire stations across the country.

Some of the most evocative items remaining in Hangar 17 are hard to classify, more than souvenirs but not quite museum pieces. A rack of bikes, a battered shovel, a dented file cabinet bursting with papers.

In a shadowy corner, Johnson unlocks a door to a smaller, climate-controlled room. Inside, the contents are stunningly unexpected: giant statues of Bugs Bunny, Elmer Fudd and the Road Runner loom, smoke-damaged but grinning, the remnants of a Warner Bros. store in the World Trade Center. A sign in golden script reads “That’s all Folks!”

“Isn’t that something?” Johnson asks. “It brings a human element to all the inanimate objects.”

It’s her favorite part of the hangar, though she can’t say why. They would hardly seem to be important artifacts — yet they are. Later, it comes to her, and she sends an e-mail. “Wreckage becomes relic when it is associated with people and experiences that brought you joy,” she writes.

* * *

You can take the cross out of the World Trade Center. But can you take it out of someone’s skin?

Tattoo artist Pete Dutro was just another downtown subversive before 9/11. After it, he became a full-fledged New York patriot.

Once he cleaned his store, MacDougal Street Tattoo Co., of ash, he went to Ground Zero. As he took in the scope and the stench, he had “a man cry.” He decided to help in the only way he knew: He offered free tattoos to the guys working there.

He started with a few cops and firefighters, who came for small sticker tattoos of American flags or names of the fallen. Then they came in droves, asking for something else.

“We started doing the cross,” Dutro says.

He figures he etched at least a thousand crosses into various bodies. He did 10 or 12 a day, seven days a week. While Dutrow inked their limbs, he listened to stories of where they were, who they lost. He was their therapist, their confessor. “They wanted to make sure they never forget,” he says. “It was a physical manifestation of the pain that they went through. Indelible.”

Eventually, the demand for cross tattoos ebbed. But it took a while. Throughout the long recovery effort, the cross stood at Ground Zero, symbol for the forlorn. For 10 months, Father Brian conducted services there every Sunday. He performed a windy, freezing midnight Christmas Mass, with the Host flying off the plate. He performed a Mother’s Day Mass, a Father’s Day Mass.

He never counted how many of his congregants were Catholic, or even Christian.

“I don’t know,” he says. “I never asked. And I never will.”

The cross stood throughout the even longer period of bureaucratic infighting over how to rebuild. Finally, in 2006, construction began, and to make way for it, the cross was moved temporarily to St. Peter’s Church. It stayed there until this summer, when it was taken back to Ground Zero for permanent installation.

Once again, Father Brian blessed it. By this time, it had acquired a steel plaque, affixed by a welder. “The Cross at Ground Zero — founded September 13, 2001; Blessed October 4, 2001; Temporarily relocated October 15, 2006; Will return to WTC Museum, a sign of comfort for all.”