The remains of Grace Alegre Cua were never found, and the center is the only place he feels he can visit her, he said.
"This is a sacred place to mourn. We didn't find her. This is her picture," he said. His wife was a comptroller for a Japanese bank and worked on the 83rd floor in the south tower on Sept. 11, 2001.
"I wish I could see Obama today and say thank you," said Cua, 60, of Glen Rock, N.J. "I feel satisfied that [Osama] bin Laden is dead and that he will not kill any more people."
But Cua's pain remains. "I am still single because no one will ever replace my wife," he said. Cua, who raised his two children alone, said his grieving does not cease and that "I have learned to live with it."
Today, the only joy he feels is to see his children graduate from college and knowing "that they are all right."
Tracy Larkey's husband, Robin, worked at Cantor Fitzgerald and was killed in the collapse of the Twin Towers.
So when Larkey, 48, of Chatham, N.J., heard the news that U.S. forces had killed bin Laden, she said her feelings were "bittersweet."
She said she was "ecstatic" that bin Laden was dead but thought back to a question the youngest of her three sons, William, now 11, asked her when he was 5.
"He asked me what his father's voice sounded like."
Standing outside Ground Zero, hoping to catch a glimpse of President Barack Obama, Larkey said all of those thoughts, events and emotions caused her to join onlookers at the site.
Larkey was accompanied by William, whom she took out of school for the day. She wished she'd been able to see Obama.
And of Robin Larkey's voice? "Strong," she said. And "quite lovely."
Ennis Johnson, 41, of Manhattan, was among those in the crowd at Ground Zero. He said he was a bike messenger at the time of the attacks and had just finished delivering a package to Tower One when the first plane struck. The memory of the day is still fresh in his mind.
"It was scary," he said, adding he is skeptical that bin Laden's death means attacks will stop. "I don't think it's over."
Bill Steyer, 67, originally of Patchogue, chanted "Obama got Osama." Steyer, now of Forest Hills, said, "If you're not feeling pride as an American today, you're dead and buried."
Asked if he felt safer, he said, "I feel safe every day. I'm a New Yorker. I'm not going to let anything make me afraid to go around and do what I want."
At Trinity Place and Liberty Street in lower Manhattan, German Riviera, 57, of Brooklyn, waved a "Flag of Honor," which bore the names of those lost on 9/11. "I feel safer because we killed one man. But that doesn't mean they won't hit us again. But we'll be ready."