By Sebastien Malo

NEW YORK (Reuters) - New York's One World Trade Center on Wednesday treated invited guests to a sneak peek at the panoramic views from the observation deck atop the newly opened tower, which rises nearly a quarter of a mile (400 meters) above the streets of Lower Manhattan.

The "pre-opening" of the three-floor aerie at the crown of the Western Hemisphere's tallest building marks the latest milestone in the rebuilding of the site where the Twin Towers were destroyed in the attacks of Sept. 11, 2001.

"There's always the thought of 9/11 but you can't really think like that," said Robert Domino, a 20-year-old maintenance worker who has gone to the observatory to do cleaning work. "Going up there is a beautiful thing to experience."

One World Observatory, housed on the 100th, 101st and 102nd floors of the building that's also known as Freedom Tower, will open to the public on May 29, according to Legends, the facilities operator that runs the attraction.

Floor-to-ceiling windows offer stunning views of New York Harbor and the skyline of Midtown Manhattan, as well as seemingly endless vistas of Long Island, New Jersey and the Atlantic. On a clear day, visibility stretches for up to 50 miles (80 km), said David Kerschner, president of attractions at Legends, who hosted the preview for media and other guests.

The observatory will compete against Rockefeller Center and the Empire State Building. At 1,268 feet (386 meters), it stands a scant 18 feet (5.5 meters) above the Empire State.

But height is not the only draw, according to Kerschner, who said the observatory is also counting on high-tech bells and whistles to attract visitors.

"This is unlike any observation deck any place in the world," he said. "Because rather than being just an elevator ride up, seeing the beautiful view and an elevator ride down, we've created a 45 minute to an hour entertainment experience."

The attraction features Sky Pod, a bank of five elevators that whisk visitors to the top in 47 seconds while playing a video recreating the rise of the New York skyline. The film includes a glimpse of the old World Trade Center towers, even at the risk of evoking painful memories for many.

"We thought about it a lot," said Kerschner. "We felt that it was the most respectful way to deal with it."

Demand is strong, he added, with some 350,000 tickets already sold or reserved at $26 to $90 each.

(Writing by Frank McGurty; Editing by Eric Walsh)