Credit: Mark Lennihan/AP Photo

REPORTER'S NOTEBOOK: It was 5 a.m., and the sun had yet to rise over New York City as we hailed a cab and made our way down to Lower Manhattan. It was there - the World Trade Center complex - where 11 years ago on this day nearly 3,000 people were killed in the worst terrorist attack in U.S. history.

When we arrived at the new One World Trade Center, formerly called the Freedom Tower, the sky was still dark and the building was illuminated with red, white and blue lights. We grabbed coffee and a bite to eat before heading up to the ABC News broadcast location. It was tough not to wonder how many of those who died here on Sept. 11, 2001, began their day just as innocently.

Our crew and others packed into a small, open-air freight elevator on the skyscraper's ground level. It took somewhere between 30 seconds and a minute to lift us beyond the building's concrete foundation and up to the 22nd floor.

Significant progress has been made here since last year's memorial, but much work remains. This building, which will become the tallest in the Western Hemisphere at the symbolic height of 1,776 feet, is still very much a construction site.

There's no indication as to what might occupy the desolate space we're using today. For now there is nothing here beyond a few lights, a chalky, cement floor, windows and an unfinished ceiling. It's cold: A large fan blowing in our direction is the only means of circulation. The sound of drilling can occasionally be heard in the distance.

Out the window in front of us, we see the reflecting pools that mark the footprints of the Twin Towers - the main focal point of the 9/11 memorial. Hundreds gathered at this site even before dawn, but as the sun rose, mourners were greeted by a bright, cloudless sky, just like the one that covered New York City on this day 11 years ago.

"Sparkling in sunshine, water cascades into reflecting pools that mark the spots where the Twin Towers of the World Trade Center once stood," ABC News correspondent Aaron Katersky said, describing the scene to an audience of radio listeners. "Around those pools, the names of victims are etched in bronze parapets. Relatives treat them like gravestones and take paper and pencil to make rubbings."

Police vehicles, many with lights flashing, line the perimeter of this site. Traffic is moving at a steady pace. In the distance, boats can be seen patrolling the waters of the Hudson River.

The commemoration here is smaller than in years past, but the feeling hasn't changed. Moments of silence were observed and bells tolled just as they always have on this day, but in a break from years past, politicians and dignitaries are here without official roles; only family members are participating in the recitation of names - a tradition that takes hours to complete.

The future of this ceremony is unclear. The city is attempting to scale back on what has become an annual gathering for mourners to remember loved ones on the very site on which they died.

President Obama marked today's anniversary with events in and around Washington, D.C., while Vice President Joe Biden spoke at a service in Shanksville, Pa., where United Flight 93 crashed after passengers attempted to take control of the plane from the hijackers.