Ground zero's iconic "Last Column" unwrapped for first time in years for Sept. 11 museum display

(CBS News) "The Last Column," a key symbol of the Sept. 11, 2001, terror attacks, was uncovered at the former World Trade Center site on Wednesday. It's been wrapped in plastic and buried underground for the past four years.

The column was the final piece of the World Trade Center left standing. It was also the last artifact removed from ground zero, signaling the end of recovery efforts.

Special Section: Remembering 9-11

Joe Daniels, president of the National September 11 Memorial & Museum, said when he saw the column, uncovered for the first time since it was brought back to the site four years ago, he felt, "just a sense of happiness."

The three-and-a-half story-high, 58-ton steel beam sits seven stories beneath ground zero and the memorial pools that mark the towers' footprints. The column - which has become a kind of cornerstone for the museum - is so massive they couldn't bring it into the museum. They had to build the museum around it.

"This is one of the most important artifacts that we have," Daniels said. "It's become a symbol of strength and resilience. You can see it's adorned with messages of hope and graffiti of remembrance."

The column is adorned with messages written by firefighters from Squad 41, who, for months, couldn't reach the remains of their fallen comrades buried nearby.

Others followed suit on the column, writing messages, taping pictures and turning it into a kind of grave marker.

When it was finally removed in 2002, the beam was draped in the American flag - the same honor given to all the 9/11 victims who were recovered.

Daniels said the museum is now preserving the mementos and reapplying them to the column so they will stand the test of time.

When the museum opens in the spring of 2014, visitors will be able to see and learn about every single item written or affixed to the column - even those that tower more than 30 feet above them because of four touch-screen panels that allow you to zoom in and see individual photos and messages anywhere on the column.

Alice Greenwald, director of the National September 11 Memorial & Museum said, "All the way through the museum, we are using technology in the service of our storytelling."

"The Last Column" - part of the South Tower that withstood the 9/11 attacks - is the centerpiece of the museum. However, the museum's cavernous space - once the foundation of the Twin Towers - will also hold a number of artifacts from 9/11, from the iconic tridents from the World Trade Center's skin to the stairs hundreds of survivors used to escape the one of the buildings.

After Superstorm Sandy, the museum hall was swamped in 7 feet of water. But "The Last Column," protected by its plastic wrapping, came through unscathed. The museum has cost about $700 million to build; about $450 million of that amount was paid for by the private sector.