Rotting wooden planks, held aloft by rusty bits of wire, stretch out in front of you. You reach for a railing to steady yourself, but all you find are two threadbare ropes. The howling wind blows the rickety footbridge from side to side. Somewhere below you lies the forest floor—you don’t even know how far.All bridges serve a purpose, whether utilitarian or inspirational. And some of them, like Musou Tsuribashi—this shaky, 50-year-old crossing in southern Japan —add a distinct element of fear. But you don’t have to be in a remote part of the world: scary bridges exist everywhere, in all shapes, sizes, and heights. And crossing over them can be the ultimate in adventure travel.Surprisingly, not all of these bridges are old and dilapidated. Take the Mackinac Bridge, which connects Michigan ’s Upper and Lower peninsulas. The wind here can reach speeds of 30 mph, leading to white-knuckled drives across its five-mile-long span. It can be so scary that some people simply won’t go. So the Mackinac Bridge Authority will drive your car for you…for free. In the past year, it has assisted almost 1,400 drivers—and plenty of similar programs exist around the country.Is this an irrational fear? Not necessarily. Gephyrophobia—the fear of bridges—is an accepted psychological diagnosis. Dr. Michael R. Liebowitz, founder of the Anxiety Disorders Clinic at the New York State Psychiatric Institute, told the New York Times that the fear of crossing bridges is very common (if not as well known as, say, the fear of flying). It also “carries a stigma,” says Liebowitz, even though bridges have been known to collapse, like the interstate highway bridge in downtown Minneapolis in 2007.But unlike gephyrophobes, many courageous (or foolhardy) travelers seek out hair-raising bridges just for the thrill. The bridges along the route to Colombia ’s National Archeological Park of Tierradentro are a good example. Though there are safer routes via bus from La Plata, some thrill-seekers choose to ride motorcycles over slippery bamboo crossings deep in the mountains, where one wrong move could mean plunging into a turbulent river.So get ready to face your fears—or maybe find your next adventure—with our list of the world’s most petrifying bridges.