CHICAGO - The view from the tallest skyscraper in the Western Hemisphere just got better.

Some may experience a floating sensation when stepping into one of four glass boxes that jut out from the indoor observation deck at the Sears Tower.

"At first I was kind of afraid but I got used to it," said Adam Kane, 10, a visitor from Alton, Illinois, as clouds drifted past. "Look at all those tiny things that are usually huge."

"The Ledge," unveiled on Wednesday, invites visitors to step onto a 1-1/2 inch-thick glass floor suspended 1,353 feet in the air.

"We did studies that showed a 4-foot-deep enclosure makes you feel like you're floating since there's only room for one row of people, not two," architect Ross Wimer said. The enclosures are 10 feet high and 10 feet wide.

The popular deck attracts 25,000 visitors on clear days. They each pay US$15 to take an elevator ride up to the 103rd floor of the 110-story office building that opened in 1973.

Architects considered creating an open-air deck, like the one atop New York's Empire State Building, but the rush of air that would have been created could compromise the skyscraper's mechanical systems, Wimer said.

(Reporting by Andrew Stern, editing by Alan Elsner)