One of the most impressive bridges at Foxfire Mountain Adventure Park is a swing bridge. It’s four feet wide and more than 400 feet long—that’s longer than a football field! The bridge actually swings—in a very safe and sturdy way—when you walk across it. The bridge is anchored by more than 30 tons of concrete on either end, and it can hold more than 24,000 pounds.

The bridge was built in 2012 to celebrate the park’s 40th anniversary. It’s a true feat of engineering, and it has become a must-see attraction for visitors. But despite how cool the bridge is, it’s not for everyone. It requires a certain amount of courage to traverse it, and those with a fear of heights aren’t encouraged to do so.

Those who can’t quite muster up the courage to walk over the bridge are welcomed with a picturesque view of the surrounding mountains and valleys, but they’re not permitted to step foot on the bridge itself. In its commercial form, bridge swinging is a thrill activity similar to bungee jumping where people swing to-and-fro like a pendulum instead of up and down like a yo-yo. Large sums of money are paid to people who successfully complete the stunt. Bridge swinging in its amateur form involves fixing a rope to the railings and crossing over to the far side, then swinging it high enough for someone on the other side to catch it.

But even when the bridge isn’t being used for thrills, there’s still a lot to see and do. The bridge is a popular picnicking spot, and people visit for its aesthetic value as well as for its historic significance. It’s also a great place to take photos and get some perspective on the surrounding area.

The Mile High Swinging Bridge on Grandfather Mountain in North Carolina was nicknamed “mile high” because it sits a full mile above sea level (that’s 5,280 feet!). The bridge is accessible with a ticket to the mountain and is the highest suspension bridge in the United States.

According to Tom Olson, an expert in the use of physics to solve mysteries in art and history, the bridge’s destruction was caused by something much less exciting than resonance. He says that every object has a natural frequency, and when waves vibrate around the bridge at that frequency, it can cause the bridge to sway. The same is true for pedestrians, who have an instinctive tendency to synchronize their steps with the bridge’s natural rhythm and with each other. This can be dangerous when the bridge’s natural frequency is excited by a crowd of pedestrians walking together.