Chicago Skydeck on 103rd floor begins to crack under family

Moments before a family vacationing from California walked out onto the Skydeck on the 103rd floor of the Willis Tower in Chicago they say they were reassured by staffers that the window floor was unbreakable.

Before they could count to 103, however, they say they started to hear the floor crack.

'Crazy feeling and experience,' Alejandro Garibay, a tourist, told NBC Chicago. A picture posted on its website shows shattered glass that was the floor of the Skydeck.

'I walked them (staff) over so they could see and they were totally shocked and asked us to step away,' Garibay said.

There are four of these glass enclosures called The Ledge, which opened in 2009, which gives tourists the feeling of standing suspended in air.

These balconies are suspended 1,353 feet in the air and jut out four feet from the building. They're actually more like boxes than balconies, with transparent walls, floor and ceiling. Visitors are treated to unobstructed views of Chicago from the building's west side and a heart-stopping vista of the street and Chicago River below - for those brave enough to look straight down.

Officials from the Willis Tower did not respond to the station for comment.