Six years of construction. 37,000 tons of steel. A 186-foot concrete base. Over 100 floors. An eventual height of 1,776 feet.

The numbers behind One World Trade Center — the building formerly known as the Freedom Tower — are impressive. But all you really need to know about that still-unfinished building is this: As of tonight, it will again be New York City’s tallest skyscraper.

Good Morning America‘s George Stephanopoulos traveled to the tippy-top of the tower this morning, taking a perilous journey that involves two elevators and a series of sheer vertical ladders. (So far, lifts only go to the tower’s 90th floor.) After climbing 1,200 feet, he chatted with a few of the crane operators who have been working to build 1WTC steel beam by steel beam. Their involvement is especially poignant because each was an eyewitness to the devastation of 9/11 — and according to one, “not a day goes by” that he and his coworkers don’t think about the events of that catastrophe.

Take a look at Stephanopoulos’s journey to the top of Manhattan’s skyline in the video below — and if you’re an emotional person, you might want to get a box of tissues handy.

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