The man behind the rebuilding of 9/11's Ground Zero

(Reuters) - Developer Larry Silverstein signed a $3.2 billion 99-year lease on New York's World Trade Center six weeks before the Sept. 11 attacks in 2001. He recalls the smoldering ruins of the Twin Towers as "probably the worst day of my life."

Now, as the 20th anniversary of 9/11 approaches, Silverstein says that what remains are his memories of the goodness of New Yorkers in the days that followed.

"Thousands of New Yorkers decided to come down to the site. ... They simply volunteered to put themselves in terrible danger ... and endeavor to rescue people," he said.

"It was New York at its best, at its finest. And I was so proud to be a New Yorker. I was so proud to know that these people were coming down to help the best they could. It was something that I could never forget."

The Twin Towers and surrounding buildings were destroyed by al Qaeda hijackers of two U.S. airliners, killing 2,753 people.

Silverstein, 70 years old at the time, was ready to retire.

"I said to my wife, 'Now that we've got the brass ring ... whatever you want to do that we delayed all these years doing, we can do.' It didn't turn out that way," he said. "Such is life."

Silverstein's agreement covered the management and operation of the Twin Towers, Four and Five World Trade Center, and approximately 425,000 square feet (nearly 40,000 square meters) of retail space. It also gave Silverstein, as leaseholder, the right and the obligation to rebuild the structures if destroyed.

Silverstein immediately decided to rebuild after the 9/11 attacks. A protracted legal battle ensued with insurers.

In 2007, New York's then-Governor Eliot Spitzer helped to end nearly six years of legal battles that seven World Trade Center insurers had with Silverstein.

A plan was born, and a lengthy metamorphosis turned the disaster zone into a giant pit, then a walled-off construction site, and finally, some $25 billion later, a tourist attraction and business center with three skyscrapers, a transportation hub, a museum and a memorial.

Silverstein thought the entire site would be rebuilt by 2020, but that changed after the planned anchor tenant for 2 World Trade Center pulled out.

"We're still not finished," he said. "But since I'm only 90, no rush. I have plenty of time."

(Reporting by Roselle Chen and Hussein Al Waaile; Writing by Mark Porter; Editing by Howard Goller)