A 70-feet-tall steel column, that literally formed the backbone of the twin towers of the World Trade Center in New York, made a return to the original site and would be part of a memorial to the Sep 11, 2001 terror attack.

Salvaged from the debris, the 52-tonne three-pronged column that once formed the base of the towers was lowered into place at the 9/11 memorial, where it will stand as a poignant reminder of the missing skyscrapers, the New York Post reported Wednesday.

A second trident would also be put there as part of the memorial.

'The tridents are visual references to the towers that once stood at the World Trade Center,' New York Mayor Michael Bloomberg was quoted as saying.

The tridents will be located in the visitor's centre, a glass building that will serve as the entrance to the 9/11 museum.

'The tridents will stand as a powerful message of hope and endurance in the face of tragedy,' memorial president Joe Daniels said.

Meanwhile, the White House has announced that Vice President Joe Biden will attend the 9/11 ceremony in New York Saturday, while President Barack Obama will be at a ceremony at the Pentagon.