• The world's scariest bridges are known for their steep slopes and stomach-churning heights.
  • Some bridges that may look terrifying are actually relatively safe to cross, like the Sidu River Bridge in China.
  • Others, like the U Bein Bridge in Myanmar, may be on the verge of collapse.

On the morning of August 14, a fierce thunderstorm struck the Morandi Bridge in Genoa, Italy, sending the decades-old structure tumbling to the ground.

In the years leading up to the collapse, engineers had warned that the bridge might not be structurally sound, but the timing was ill-fated. Just as the bridge's maintenance company began to embark on repairs , the storm derailed their efforts.

Read more: 7 of the most dangerous roads in the world

Determining whether a bridge is "safe" is a complicated question. In the United States, one of out every ten bridges is considered "structurally deficient," meaning it's in need of significant maintenance or repair. That includes the Brooklyn Bridge , which carries more than 100,000 vehicles each day.

While it's difficult to tell if a bridge is dangerous just by looking at it, a few bridges are downright terrifying to cross no matter their stability.

We've rounded up some of the scariest bridges in the world, which are notable for their stomach-churning heights, rickety guardrails, and steep slopes that seem to defy engineering logic. Take a look.

To build the Langkawi Sky Bridge in Malaysia, a construction team had to lift the structure by helicopter.

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At 410 feet long, it's the longest curved bridge in the world.

It only took six months to build the Royal Gorge Bridge in Colorado, which hovers more than 950 feet above the Arkansas River.

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Royal Gorge may have lost its title as the world's highest bridge , but it's still the tallest in the US.

The Cloud Bridge at Daedunsan Mountain in South Korea slopes above a narrow canyon.

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"I felt it swaying as the gusts of wind came up and wrapped around the peaks," one travel blogger wrote.

The Aiguille du Midi bridge in the French Alps is accessible by cable car.

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Visitors can also travel to the summit of the mountain, which is more than 12,000 feet tall.

It costs about $20 to cross the Zhangjiajie Glass Bridge in China.

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As its name suggests, the bridge has a transparent walkway .

Japan's Eshima Ohashi Bridge looks like a rollercoaster.

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The bridge appears incredibly steep from certain angles, but the incline for drivers is somewhat gradual .

The Titlis Cliff Walk in the Swiss Alps is Europes highest suspension bridge.

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A spokesperson for the nearby Titlis Engelberg ski resort told NBC News that it was "impossible to fall from the bridge."

To get to the Trift Bridge in Switzerland, visitors have to take a cable car, then hike around 1.5 miles uphill.

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The bridge is only open to pedestrians .

There have been a few deaths on the Capilano Suspension Bridge in Vancouver.

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An American high school student died in 2010 after climbing over a railing.

Construction workers had to use a rocket to build the suspension cable on China's Sidu River Bridge.

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The bridge may look terrifying, but it's able to hold more than 43 million tons of weight.

Ireland's Carrick-a-Rede Rope Bridge offers a shaky pathway to a small island.

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The bridge is relatively short around 66 feet.

Ghana's Kakum Canopy Walk isn't for the faint of heart.

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The walkway is actually a series of seven bridges that stretches across multiple tree tops.

The Hussaini Hanging Bridge in Pakistan was once so unsteady, it washed away and had to be rebuilt.

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It's been dubbed the most dangerous bridge in the world.

Nepal's Hanging Bridge of Ghasa is used to herd cattle.

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Animals are a common sight on the bridge , but pedestrians are also welcome to cross.

New Zealand's Kawarau Bridge is the world's first commercial bungee jumping site.

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Daredevils can take the plunge from more than 140 feet above theKawarau River.

The teakwood pillars on Myanmar's U Bein Bridge are decaying, leading to concerns that it may one day collapse.

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The bridge has been around fornearly 120 years.

China's Tianmen Skywalk is only 3 feet wide.

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At 4,700 feet above ground, the glass skywalk offers a chilling view of the Zhangjiajie National Forest Park.

The Windsor Bridge in Gibraltar is located along a path called "Thrill Seekers Trail."

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The bridge opened in 2016 , so its construction is fairly new, but visitors must be brave enough to walk above a 164-foot-deep gorge.

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SEE ALSO: The most structurally deficient bridge in every US state