UNDATED (CNN) -- As "One World Trade Center" nears completion, a reminder of the collapse of the original towers has apparently come to light.
Efforts are underway to retrieve what's believed to be a piece of one of the doomed planes. It wasn't found until a few days ago. it may have been hiding there for more than 11 years.
The discovery of what authorities believe is the landing gear of one of the two planes that crashed into the twin towers on 9/11 is remarkable.
For one, the sheer size of the piece: 5 feet by 4 feet by 17 inches. then, there's the location of it: in a narrow space just 18 inches wide, wedged between two buildings; one of them, the site of that controversial Islamic community center.
The part was first discovered on Wednesday by surveyors who saw something suspicious and alerted authorities. NYPD Commissioner Ray Kelly says, "They look at it, they're not certain what it is, our emergency service unit responds. As you get closer on the part, you see a serial number and you see the word, 'Boeing,' before that serial number."
It is then that investigators realize what they have, but how did it get there? Kelly says, "It certainly is possible that it was wedged down there and went directly into the alley. Depends on the angle at which it hit. We're also looking into the possibility that it was lowered by a rope."
If you look closely at a photo, there is clearly rope tangled in the wreckage, but why would anyone deliberately put it here, if that is indeed what happened? Nobody knows.
What is clear is that investigators will be back on Monday for about a week, to look for toxic material and human remains.
Jim Riches is a retired deputy chief at the New York City Fire Department. His son, Jimmy, was also a firefighter, who on 9/11, ran bravely into the north tower to try to save lives. The 29-year-old never came out.
Riches says, "I stayed down there from September 11th, that day, and dug on my hands and knees until we found him on his brother's birthday, March 25, 2002. And me and his three brothers carried his body out of Ground Zero. And that's what we hope for the 1000 other families who've never recovered anything, to at least be able to go to a cemetery and leave some flowers.
One of the questions investigators will want answered is if this piece is indeed from 9/11, which plane did it come from? Did it come from American Airlines flight 11 which crashed into the north tower? Or United flight 175 which slammed into the south tower?
Another question is: how will they remove this massive piece of fuselage from this narrow space?
Will the buildings have to be demolished? For now, those questions remain unanswered.