New York ? For many of us, the World Trade Center has existed in two states.

It was there. Then it was taken from us.

But there is much more to the story of the Twin Towers, as viewers will find in “The Center of the World,” premiering at 8 p.m. Monday on PBS.

In this three-hour “American Experience” documentary, filmmaker Ric Burns explores why, in their absence, they command an inescapable presence in our lives. But he also reaches back nearly a half-century to tell the little-known saga of how the buildings came to be.

“The Center of the World” is the eighth and final chapter of “New York,” Burns’ 17 1/2-hour epic urban portrait spanning 400 years, whose first installments aired in November 1999, then was meant to conclude in late September 2001.

“This final chapter,” says Burns in his office on Manhattan’s Upper West Side, “was compelled by the events of Sept. 11, 2001.”

Until that terrible morning, he, along with much of the Western world, was blind to much of the meaning of the towers. But no one who beheld their destruction could fail to see the awful truth, he says — or fail to feel implicated.

“I don’t mean feel guilty of anything. But we knew that it had happened because of political, cultural, ideological conflicts which are part of the world that we are all part of.

“These were the two biggest buildings in the world for a while, and they were hiding in plain sight.” Then, when they fell, “it was an instant, terrible reminder of the solipsism that makes New Yorkers so worldly and unworldly at the same time. This film is an attempt to go back and look at this icon, which was both the most and least worldly thing in New York.”

The twin towers of the World Trade Center burn behind New York's Empire State Building in this Sept. 11, 2001, file photo. The Trade Center, fated to become one of the most controversial structures of the 20th century, is the focus of The

The film calls the towers “the mightiest and most ambivalent monuments of their age,” and, indeed, nearly any conclusion one can draw about them invites a counterclaim. They were an oversized eyesore and they were magnificent; a real estate fiasco and a commercial triumph.

And that is how they stood, aligned in a face-off of antagonistic forces — until the “perfect, almost achingly beautiful late summer morning” when, literally out of the blue, everything changed.

The film’s final one-third covers all-too-familiar events that some of us may choose not to revisit. But, as with the seven chapters that preceded it, “The Center of the World” is an eloquent, arresting film.