Heads of state from around the world will join in the lighting of an eternal flame September 11 at The Sphere, a sculpture that once stood at the base of the World Trade Center towers, but is now serving as a temporary memorial to the victims of last year's terrorist attacks.

The foreign leaders, in New York for the United Nations General Assembly, will assemble at sunset in Lower Manhattan, where the eight-meter high steel and bronze globe rests. The sculpture was created by German artist Fritz Koenig as a tribute to "peace through world trade." The 20,000 kilogram Sphere was a prominent feature on the two hectare plaza of the World Trade Center.

The Sphere was badly damaged in the September 11 attacks. Falling debris created a large hole in the top and a bible, an airline seat, and papers from top-floor offices were found inside. But the sculpture was sufficiently intact to become a makeshift memorial to the victims. Peter Rinaldi, the general manager of the World Trade Center site, calls the Sphere's recovery miraculous. "That was one of the few times we were able to reconstruct or rebuild something, so that was kind of uplifting," he said. "Having worked on the site, taking things apart and looking for people, the one thing we did do on March 11, we reconstructed that sphere."

Fritz Koenig, now 77, flew in from Germany to supervise the reconditioning of his 1971 work.

Of the hundreds of artworks once located in or around the World Trade Center, The Sphere is one of only two that survived. Dozens of bronze sculptures by Auguste Rodin are gone, as are paintings by Pablo Picasso, David Hockney and Roy Lichtenstein.

In addition to the lighting of the eternal flame, the ceremony at the Sphere will feature a reading by New York City Mayor Michael Bloomberg, of President Franklin Roosevelt's Four Freedoms.