WTC Steel Beams to Be Installed for 9/11 Museum

Visitors photograph the World Trade Center construction site Sunday, March, 12, 2006, in New York. Initial work begins Monday, March 13, 2006, on the Sept. 11 memorial at ground zero.
Steel columns salvaged from the rubble of the World Trade Center are heading back to ground zero.

Two 70-foot columns taken from the wreckage of the north tower are being permanently installed Tuesday at the entrance to the Sept. 11 museum.

The 50-ton columns have three prongs and are known as tridents. They made up the facade at the tower's entrance. For the past few years they've been kept at a hanger at John F. Kennedy International Airport with other material recovered from the destroyed World Trade Center site.

The $45 million museum is being built below the 8-acre memorial plaza. It's set to open next year.