CHICAGO - Visitors to the top of the tallest building in North America soon won't be able to avoid looking straight down.

The Sears Tower plans this summer to add four enclosed glass-bottomed balconies jutting out from the building's 103rd floor Skydeck - offering a view of 1,353 feet down.

Each of the balconies - all on the tower's west side - will be able to hold about five tons and the glass will be a half-inch thick.

Randy Stancik, Skydeck general manager, says he was inspired by glass-floored thrills at the Grand Canyon and Toronto's CN Tower.

The balconies will extend about 4 feet from the observation deck, part of a multimillion dollar renovation plan coinciding with a renaming to Willis Tower.

On the Net:

http://www.theskydeck.com