Observation deck of the rebuilt World Trade Center, also known as Freedom Tower, opens to the public next Friday
You can just about make out the curvature of the earth.
That should be a sight reserved for planes, not the new observation deck at New York's reborn World Trade Center.
Depending on the weather, you can see for 80km, said Mr David Checketts, chairman and chief executive officer of Legends, the company which operates the observatory.
The observation deck, which opens to the public next Friday, is testament to the resilience of New Yorkers, said Mr Checketts.
The tallest office building in the Western hemisphere, the Trade Center (right), also known as Freedom Tower, welcomed its first tenants last year.
Built on the site of buildings destroyed in the Sept 11, 2001 attacks, it was constructed to a total height, antenna included, of 1,776 feet (541m), to honour the signing of the US Declaration of Independence in 1776.
Operators expect three to four million visitors a year will take in the 360-degree views at 380m of sights like the Statue of Liberty, to Central Park, Brooklyn Bridge and New Jersey to the west.
It was a panorama that many never expected to see again, AFP reported.
"We are back, 100 per cent," New York Mayor Bill de Blasio told CBS television in a special programme broadcast atop the observation deck, which covers the 100th, 101st and 102nd floors of the gleaming glass tower.
"It's a great moment, it really says that we have turned the corner once and for all, and those that sought to attack us, lost once again."
Mr Checketts said: "This is like a fist bump, saying we put it back up and the construction and restoration of neighbourhoods around downtown make it really feel like New York is back."
The elevator - one of the quickest in the world - takes 47 seconds to reach the 102nd floor and is a journey in itself.
Floor-to-ceiling LED technology provides visitors with a virtual time-lapse that recreates the development of the city's skyline from the 1600s to the present.
Once in the observatory, visitors are welcomed with a two-minute video that combines time-lapse shots with abstract textures and patterns to present the rhythm and pulse of the city in 3D.
On the 101st floor there is a restaurant, a grill and a cafe, as well as a place to have photographs taken against the backdrop.
Those who do not get queasy with vertigo can step out onto a sky portal - a 4m-wide disc that uses real-time, high-definition footage to give a view of the streets below.
Visitors are subject to tough security measures similar to those at airports, or indeed at other public buildings in New York.
It is perhaps the strongest and most secure building on the earth, said Mr Checketts.
The observatory will compete with two other popular viewing sites in the city: the Empire State Building, which stays open until 2am and which last year welcomed more than three million visitors, and the Rockefeller Center, visited by 2.5 million and open until midnight.
Standard entry to the observatory is US$32 (S$43) for adults, US$30 for seniors and US$26 for children. It will be open seven days a week from 9am to midnight until Sept 7, and from 9am to 8pm until May 5, 2016.
It is free for relatives of the victims of the Sept 11, 2001 attacks and to first responders to the disaster.
In total, 2,753 people were killed at the World Trade Center site when Al-Qaeda hijacked two passenger jets and flew them into the Twin Towers.
This article was first published on May 22, 2015.
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