Tourists at Chicago’s Willis Tower were left terrified Monday evening, when glass coating cracked beneath visitors’ feet on the building’s Skydeck on the 103rd floor.
One witness described hearing a ‘boom’, before noticing the glass had ‘splintered into thousands of pieces’, according to CBS 2.
A mother and her two children were reportedly standing on the deck at the time.
The trio were taking in the views from Willis Tower, which, at 1,451 feet, is the tallest building in the Chicago and the second-tallest in the United States.
The Skydeck boasts protruding glass ledges that allow tourists to look directly down at the streets below.
No one was injured in the incident, and a spokesperson for the Tower said no visitors were ever in danger as the glass is part of a protective layer of coating over the top of the Skydeck.
However, an eyewitness say the incident was enough to keep them indoors.
Visitor Karly Pintado told CBS 2: ‘I’m scared of heights in general so when I saw that happen, I was like “Nope, not going on.”‘
Pintado’s husband, Jesus, filmed the commotion following the event, with many tourists seen looking on in shock at the shattered glass.
It’s not the first time that protective glass on the Skydeck has cracked while the attraction was open for business.
Back in May 2014, a protective layer of glass shattered on the same ledge window.
However, one public relations expert told The Atlantic at the time: ‘The [glass] 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.’
Following Monday’s incident, the glass panel was quickly replaced, and the Skydeck at Willis Tower remains open.
The skyscraper – formerly known as Sears Tower – was completed in 1973 when it surpassed the World Trade Center as the tallest building in the world, a title held for almost 25 years.
The Skydeck first opened in 1974 and quickly became a tourist attraction. More than one million people visit each year.