RUTHFULLY YOURS

National September 11 Memorial Foundation officials last week introduced a cavernous, $700 million underground museum to the media. Opening in the spring, the museum at the former World Trade Center site will exhibit many irreplaceable, authentic artifacts from that terrible day. One of the pieces on display will be the New York Fire Department’s Engine 21, the half-burnt out rig that my brother, Capt. Billy Burke Jr., and his men rode down to the burning buildings on 9/11.

“Artifacts have the power to connect us to history with an unmatched immediacy,” said Alice Greenwald, director of the museum, during the media tour. Joe Daniels, president of the memorial foundation, added that “these artifacts will preserve the powerful story of 9/11 for generations to come.”

True enough, but then why isn’t one of the most significant objects from 9/11 going to be included, just as it was not used above ground for the National September 11 Memorial with its waterfalls and reflecting pools?

For 30 years the Koenig Sphere, a 25-foot-tall bronze globe sculpture by German artist Fritz Koenig, stood in the center of the WTC as a symbol of world peace. Office workers and visitors of every nationality lunched around it or posed before it for photographs. On Sept. 11, though badly damaged, the Sphere was found in the ruins still intact—an emblem of world peace had been transformed into a symbol of American strength and resiliency.

On March 11, 2002, the six-month anniversary of the attacks, the Sphere was installed in lower Manhattan at Battery Park as a “temporary” memorial. Americans might have assumed that once a 9/11 memorial was completed the Sphere would be moved from its temporary home and restored to the WTC site—possibly even as the centerpiece of such a memorial.

It didn’t happen. Instead, we have a memorial with waterfalls and trees mean to encourage a sense of healing, and deep pools in the footprints of the towers called “Reflecting Absence.”

One absence in particular: Koenig’s Sphere. Today, as millions visit the National September 11 Memorial, the Sphere still sits in Battery Park. Fenced off from anyone who might want to visit this artifact of the 9/11 attacks, the sculpture sits in the middle of a construction site, surrounded by tarp, backhoes and sewer pipes. Pigeons roost in it; bird droppings cover it.

Twelve years after the attacks, the Sphere’s future remains uncertain. The Battery Park Conservancy wants it out; the National September 11 Memorial Foundation, led by Mayor Michael Bloomberg, does not want it back.

Imagine the USS Arizona Memorial without the USS Arizona or the Hiroshima Peace Memorial without its centerpiece, a skeletal dome that survived the atomic-bomb attack.

The indifference of the National September 11 Memorial Foundation to the fate of the Sphere is hard to comprehend. The organization must be aware that in public forums about the memorial, before a design was even chosen, New Yorkers called for the return of the Sphere to the WTC site. More recently, thousands of people, including 9/11 family members, survivors, first responders and Ground Zero workers, have signed online petitions urging the restoration of the Sphere to its rightful home.

Patrick Foye, the executive director the Port Authority of New York & New Jersey, which is in charge of rebuilding the WTC site, has called the return of the Sphere “appropriate.” In the 9/11 attack, his organization lost 84 people. The Fritz and Maria Koenig Foundation of Landshutt, Germany, has called for the Sphere’s return, so that the sculpture can serve a symbolic function “as a victim, witness and survivor.”

The memorial foundation remains unmoved. The revelation last week that the Sphere was not among the 9/11 artifacts to be displayed in the 110,000-square-foot museum is particularly inexplicable.

Next spring, I will visit the 9/11 museum when it opens, and I will pay my respects to Engine 21 in memory of my brother. But I’ll also wonder why space couldn’t have been found for a bronze sculpture that a dozen years ago inspired and comforted millions of heartbroken Americans when it was found intact among the rubble on that terrible day. And I won’t be alone.

Mr. Burke lives in New York.

A version of this article appeared September 11, 2013, on page A13 in the U.S. edition of The Wall Street Journal, with the headline: A Missing Symbol at the 9/11 Museum.