A group of tourists received the fright of their lives late Wednesday when the glass pane on the 103^rd floor of the Willis Tower (formerly known as the Sears Tower) began to crack beneath their feet.

The glass floor is part of a transparent viewing deck which allows tourists to step out and look down over Chicago.

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The tourists are a family from California visiting the windy city and they experienced terror at 1,353 ft. when they sat down to take a picture on the glass floor and realized that it had started to crack beneath them.

The incident was accompanied by the distinct sound of shattering glass, eyewitnesses said.

No one was hurt and Willis Tower staff immediately evacuated the family from the transparent deck.

Reportedly, 'the Ledge', as the glass viewing boxes are called, has a three inch glass pain meant to withstand up to five tons of weight.

Randy Stanci, a Willis Tower spokesman, tried to assure people that this sort of occurrence is normal and does not indicate that people were in danger and the Tower released a statement saying:

"The Ledge was designed with a protective coating that completely covers all glass surfaces to protect against scratches. This coating does not affect the structural integrity of The Ledge in any way. Occasionally, the coating will crack, as it is designed to in order to protect the surface of the glass."

But even though the family supposedly wasn't in any danger, they were still shaken by the experience and told news sources that they were shocked when the floor starting to crack after staffers had claimed that the panes were 'unbreakable'.

Apparently the piece of glass that cracked is only cosmetic and is not the safety glass. The broken piece is being replaced and as of Thursday all four glass ledges have been closed for what is being called a routine inspection.

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