When tourists visited the vertiginous viewing platform at Willis Tower in Chicago, the experience proved shattering.

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High above the streets, tourists are enjoying stunning views of the Windy City. It is June 2019 and sightseers have made their way up to the 103rd floor of the Willis Tower to look out at Chicago. Some daredevils then step out onto a glass ledge, which makes them look as though they are floating in the air.

A woman is leading her two youngsters out into the glass box. Once there, the transparent viewing platform allows the trio to look down at the people walking more than 1,300 feet below them. From out on the attraction called The Ledge, the kids can enjoy a unique experience in the sweeping panoramas of the U.S.’ third city.

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Then, suddenly, there is a loud crack. The surface underneath the kids’ feet has turned into a crazy paving of splinters. For a moment, it must seem to them as though they are destined to fall to the sidewalk hundreds of feet below. Terror doubtless strikes the mother as she hustles them to safety.

Image: YouTube/Storyful Rights Management

Visibly shaken, the woman and her children look in horror at the floor that they were standing on. Indeed, it probably felt that they were only short seconds from disaster. From the observation deck on the 103rd floor, The Ledge appears irretrievably ruined, in a million pieces – and the exciting experience of standing out on it has turned to quivering horror.

As one of the United States’ largest cities, it’s no surprise that Chicago draws millions of visitors every year. Indeed, it ranks second after New York City as a popular tourist draw. People therefore flock there to enjoy the classy shops, many eateries and thriving culture, but it’s perhaps the famed skyline that Chicago is most known for.

Pre-eminent among Chicago’s skyscrapers is the Willis Tower. Formerly known as the Sears Tower, the building’s 110 stories make it soar 1,450 feet above the Chicago streets. And when built, it ranked as the world’s tallest building. Indeed, it would keep that spot for a quarter century, until topped by Kuala Lumpur’s Petronas Twin Towers.

Nowadays, the Willis Tower remains second in the U.S., with One World Trade Center stretching higher, although these days the world’s loftiest structures tend to be in the Eastern hemisphere. Dubai’s Burj Khalifa towers above the rest at over 2,700 feet. Nevertheless, the bronzed beauty of Willis Tower represents the peak of Chicago’s long history in tall buildings.

In fact, upwards of a million people come to the tower every year to look out from its observation deck. And its pull is no wonder, since it’s a physically imposing structure. If you could find a pair of scales big enough to measure it, it would weigh more than four hundred million pounds.

Through that bulk runs cabling that stretches for 25,000 miles. And that’s nothing compared with the telephone connections. Amazingly, at about 43,000 miles, they would line the U.S. coast to coast as many as 15 times. It’s needed for the many people – in excess of 12,000 – that the building can house.

Originally, the need for this monster building arose because in 1969 Sears, Roebuck & Co. represented the world’s biggest retailer. And its management wanted to bring together its many workers in the Chicago region. So what other would do, given the city’s reputation for huge buildings, than a new skyscraper on the Loop’s west margin?

Sears had ambitious plans, you see, which required millions of square feet of offices to accommodate its burgeoning company. And it hired the firm of Skidmore, Owings & Merrill to design the skyscraper. Its unit that handled the plans proposed a group of nine tubes that clumped together in a square, with only a couple of them reaching more than 100 stories.

The design turned out to be groundbreaking, providing more space at a cheaper price. And its looks have been reflected in most of the highest skyscrapers ever since, including in the Burj Khalifa. The engineer responsible for the original, Fazlur Rahman Khan, has been immortalized in a sculpture that takes pride of place in the tower’s own lobby.

Construction didn’t go entirely smoothly, though. Locals worrying that the soaring tower would ruin their TV reception if it went above 67 floors sued to prevent it exceeding that height in 1972. But the television lovers of Illinois couldn’t stop the building’s progress. Apparently, the judge who threw the case out suggested that they should get “taller antennas.”

Continued lawsuits went nowhere – and the Sears Tower rose. By the time the project was finished in May 1973, it had cost $150 million, which is about $850 million in today’s money. But that’s, unbelievably, something of a bargain. That’s right: the Taipei 101, for instance, the loftiest in the globe when it opened in 2004, cost over $2 billion in 2019 dollars.

However, increased competition in the retail market knocked Sears’ growth, and it couldn’t gain the tenants that it had planned for. When a big law-firm tenant moved out, it spelled the beginning of the end for the retailer – and it too started to shift out of the tower in 1992. Two years later Sears was ready to sell and found a buyer in AEW Capital Management.

Owners came and went, although the building retained the Sears name thanks to the retailer’s ownership of naming rights. But in the 2000s it suffered a major blow, as worries about potential acts of terrorism scared tenants away. Indeed, five men would go to jail for their part in a plot to destroy the tower. There were questions, nonetheless, about how solid their designs actually were. However, the threat of a terrorist attack was in all likelihood rather hard to dispel.

Meanwhile, when London insurer Willis Group Holdings came to lease some of the tower in 2009, it requested naming rights. The building subsequently adopted its current name, Willis Tower, which it will keep until at least 2024. In 2012 United Airlines shifted its HQ into the edifice, and today it is the biggest of the tower’s tenants.

Today’s tower has also seen significant “greening,” as it moves forward with the times. One program, for instance, saw waste recycled rise from ten tons a month to 56 tons in just two years. Another initiative has promoted environmentally friendly cleaning in the building. Workers are also encouraged to bike to work and use hybrid cars.

Part of this impressive building’s attraction to visitors is that it offers the opportunity to soak up great views of Chicago. From the Skydeck on the 103rd floor, after all, it is possible to see four states of the union on a clear day. And for you braver individuals, if there’s a breeze, you’ll get to feel the tower’s gentle swaying.

For those with a head for heights, furthermore, there’s a little bit of additional adrenalin on offer. Sticking more than four feet out from the Skydeck is The Ledge, a collection of boxes made of glass. Apparently, these were inspired by the many smudges that people had left on the windows of the Skydeck as they pressed their foreheads against them.

Now, not only can visitors see the metropolis without obstruction, but there’s an added extra. The shelf that they are standing on is also made of glass, so that they can gaze down at the street if they’re sufficiently bold. What’s more, the design is made so that tourists cannot see how it’s supported, giving the strange sensation of standing in midair.

In fact, when you do stand on The Ledge – designed by the tower’s initial architects but not built until 2009 – you have 1,500 pounds of glass beneath your feet. The three glass strips can take five tons of weight, although visitors in June 2019 were given reason to doubt that. That’s because an alarming incident left them fearing for their lives.

The event occurred as a woman and her two children were standing enjoying the amazing view from The Ledge. It was a busy day for the attraction, with a decent crowd gathered at the Skydeck. The small family group who were out on the glass were just three of the more than 1.7 million people who visit the observation deck every year, mind you.

All of a sudden, the clan could not longer see through the floor beneath them. That’s because the glass that formed the base of the box seemed to have shattered into bits, leaving them terrified. However, the family were not hurt – and it seemed that they had just had an extremely lucky escape.

Visitor Jesus Pintado, who retained his wits enough to film a video of the outcome, told CBS Chicago what he’d seen. He said, “There was a woman with two kids, and they looked really pale and scared because the floor just cracked.” After the unfortunate incident, the box’s floor seemed to be holding together, but no one was volunteering to go find out for sure.

One person in particular who wasn’t willing to try her luck on the shattered glass was Karly Pintado, who was accompanying Jesus. She told CBS, “I’m scared of heights in general so when I saw that happen, I was like nope, not going on.” But, as it turns out, she probably could have done so quite safely.

That’s because what had actually broken was a protective sheet that sits over the glass itself. The protection, a bit less than a quarter of an inch thick, is designed to break when necessary to keep the glass below safe from any damage. So although The Ledge was shut down straight away, the feature reopened the next morning.

Mike Swanberg, head of the company that put the coating in, told the Chicago Tribune in 2014 that it existed so that people wouldn’t have to wear “booties” to walk on The Ledge. He said that it was swapped out every six months or so. And the manager of the Skydeck, Randy Stancik, was quick to point out that the whole idea of The Ledge is to give the “illusion that it’s not safe.”

With that in mind, Stancik explained the construction to the Chicago Tribune. He said, “We hid the railings, [and] we hid the structural steel. We want to give the illusion that it’s a little bit, ‘Can I take these two steps out of the building?’” So there’s mercifully method behind the madness!

It’s not the first time that the floor has developed cracks either. Back in May 2014, visitors were likely shocked out of their skin when the coating gave way. This left tourists a chance to snap a photo of the glass, while in the meantime Willis Tower employees “fixed” the issue. Albeit, this solution involved the rapid application of a rug.

Thankfully, on this occasion too, despite the scary appearance of the damaged coating, no one was ever in any danger. But you’d presumably struggle to convince the party of tourists who’d been on the glass that when they heard it crack. For his part, Illinoisan Tony Saldana had taken his Californian cousins, the Garibays, to pose for pictures on The Ledge.

Gripped by fear, Saldana moved fast. He told local news station ABC7 Chicago at the time about the terrifying experience. The sightseer said, “All we see is the glass shattering. We’re thinking the whole thing’s coming down. We’re thinking we’re about to fall 103 stories. I completely freaked out, [and] I hopped as far as I could. I ran to the other side of the building trying to get as far away as I could from it.”

Cousin Alejandro Garibay confirmed to local news outfit NBC Chicago in May 2014 that he’d had a “crazy feeling and experience.” And he explained what it had been like to ABC7 Chicago at the time too. He said, “As soon as I put pressure on my palm to lift myself up, I just hear it, and I feel the glass just shatter. You hear a noise, kind of like stepping on ice.”

Despite the visitors’ understandable fears, the company that runs the Skydeck promptly pointed out that nothing out of the ordinary had happened. It tweeted at the time, “This coating does not affect the structural integrity in any way.” And its spokesperson confirmed to NBC Chicago, “Occasionally, the coating will crack, as it is designed to in order to protect the surface of the glass.”

Meanwhile, Skydeck head honcho Stancik confirmed that everyone had remained safe. He told ABC7 Chicago, “Never at any time was anybody in any jeopardy here.” As for the protective surface, he said, “It did what it’s supposed to do. It’s designed to crack on those rare situations where there’s some kind of impact to protect the structural piece below.”

Indeed, after the 2014 happening, the attraction did not even close. Apparently, Skydeck was so confident that it was safe that it just left the bit of carpet in place and carried on as normal. The broken covering would later be exchanged for a new layer. But as far as tourists who wanted to get their Chicago views were concerned, the show went on.

Not everyone who had missed out because of the cracking was game enough to go out onto The Ledge, however. Tatjana Thiele decided against a return visit. She told ABC7 Chicago, “They offered to give us a refund for the tickets to go back here tomorrow. But I don’t think we’re going to do that. We’re going to go to the Hancock building.”

Meanwhile, after the 2019 incident, some Twitter users seemed unwilling to risk The Ledge. One user told a friend, “And you wonder why I would never stand on that deathtrap.” The pal responded, “[Oh my God that’s] my worst nightmare. I told you it was a bad idea.” Another user shared the same sentiment, who simply posted, “Oh hell no!”

Some are made of sterner stuff, though. ABC7 Chicago demonstrated this in 2014 when it spoke to Skydeck patron Justin Alford. He said, “Now it makes it even more exciting, so we’re ready to get up there.” And he showed no fear of the bottom of the box falling out. Yes, he told the news station, “If we need a parachute, we’ll buy one on the way up.”

Indeed, Saldana added that he might just give it another go once he’d calmed down a bit. And he said, “I believe I will. I’m going to give myself time, obviously. I’m still shaking if you can see.” Certainly, one way or another, the Chicago Skydeck promises its visitors an experience to remember.