The World's 8 Scariest Viewing Platforms

Is Step into the Void, a new 12,650-foot (3,856-meter) perch in the French Alps, the scariest?

A person stands in the 'Step into the Void' installation in the French Alps.

"I must have torrents, rocks, pines, dead forests, mountains, rugged paths to go up and down, precipices beside me to frighten me," wrote Jean-Jacques Rousseau of his love of rambling in the French Alps. "The odd thing about my liking for precipitous places is that they make me giddy, and I enjoy this giddiness greatly, provided I am safely placed."

Rousseau wasn't alone in his fondness for precipitous places and giddy feelings. All around Europe, 18th-century ladies and gentlemen on the "Grand Tour" were scrambling up mountains, peering into abysses, and standing on the edges of cliffs in a quest for what they called "the sublime"—magnificent views that inspired and terrified at the same time.

Some things never change. Three centuries later, it seems we still find something, well, sublime, about going up high and scaring ourselves with a vertigo-inducing view.

And thanks to modern engineering, we can do it in heart-stopping ways that Rousseau and his fellow 18th-century romantics would never have dreamed of: from high-tech viewing platforms perched precariously over the rims of precipices, on the ledges of skyscrapers more than a thousand feet above the sidewalks, and at the exposed tippy-tops of communications towers hundreds of feet high.

They don't come any scarier—or more sublime—than Step into the Void, a viewing platform that opened last month on the top terrace of the 12,650-foot (3,856-meter) Aiguille du Midi, in the heart of Rousseau's old stomping grounds in the French Alps, near Chamonix.

Standing atop the sheer rocky spire of the Aiguille du Midi would be intimidating enough in its own right, but this skywalk takes the sublime to the next level, allowing you to stroll out into a clear, five-sided glass cube that extends over the edge, with nothing below your feet but a glass floor and nearly 3,400 feet (1,036 meters) of alpine air, all the way down to the glaciers below. Sublime views of Mont-Blanc and Chamonix can be had from here, but odds are that the view that will be gripping your imagination, with an icy hand, is the heart-stopping one straight down between your shoes.

Rousseau, one thinks, would have loved it—an easy 20-minute cable car ride to get there and, best of all, being "safely placed." The skywalk is built of five layers of specially hardened half-inch panes of glass and is designed to withstand winds of 140 miles an hour (225 kilometers an hour). Visitors must wear special slippers so that the floor stays clear and clean and doesn't get scratched—nothing to cloud your sense of the sublime.

Here are seven more of the world's scariest viewing platforms:

Taking a stroll over the edge of the Grand Canyon on a glass-floored walkway is not for the faint of heart. It's a long, long way down to the Colorado River from up there. If you were to fall, your first bounce would be anywhere from 500 to 800 feet (152 to 244 meters) below. The horseshoe-shaped cantilevered walkway allows visitors to stroll some 70 feet (21 meters) out beyond the canyon rim.

A dizzying view of downtown Chicago, Lake Michigan, and more than 50 miles (80 kilometers) of surrounding countryside can be had from the four glass-cubicle balconies that jut from the 103rd floor of the Wills Tower (formerly the Sears Tower) some 1,353 feet (412 meters) above the sidewalks. On a clear day you can see four states—Illinois, Wisconsin, Michigan, and Indiana. But the best time to go is at dusk, when the lights of the city are just starting to twinkle, like a great constellation spreading beneath your feet. If you have the nerve, you can arrange private breakfasts and dinners on tables set up on these glass-floored balconies—or even hold a wedding.

Billed as Europe's highest and scariest suspension bridge, the narrow walkway (barely 3 feet, or 91 centimeters, across) in the Swiss Alps spans a glacial abyss more than 1,500 feet (457 meters) deep. The bridge was built by a Swiss cable car company to commemorate the 100th anniversary of the opening of the nearby Engelberg-Gerschnialp cableway in 1913.

Torrents were high on Rousseau's list of things he craved to see in his quest for the sublime, and they don't come any more torrential than Iguazu Falls, a series of 270 seething rapids and thunderous waterfalls along Iguazu River on the border of Argentina and Brazil. "Poor Niagara!" Eleanor Roosevelt is said to have exclaimed when she saw it. A suspended walkway above the surging waters as they tumble over a 820-foot (250-meter) drop gives a sense of giddy horror of what it might be like to go over that yourself.

Taking a stroll along a footpath nearly 4 feet (1.2 meters) wide wouldn't seem to offer much in the way of challenge or thrills—after all, when was the last time you lost your balance and toppled over while trying to walk down the middle of a sidewalk? But put that same sidewalk 632 feet (193 meters) above the streets of Auckland, New Zealand, atop the observation deck on the city's Sky Tower telecommunications spire, and suddenly its width is going to seem as precarious as a gymnast's balance beam. Visitors are double-tethered for safety and obliged to wear coveralls to be sure that nothing falls out of their pockets and injures anyone below. There is an option to leap from the walkway as well. The stroll along the walkway is said to be scarier than jumping because you are out there, exposed, for much longer and the thrill of the sublime has a better chance to play on your mind...

Scary viewing platforms needn't be all hard angles, glass, and steel. Norwegian architects Tommie Wilhelmsen and Todd Saunders designed an elegant and wonderfully heart-stopping one using classic Scandinavian timbers and stylishly curving lines. It overlooks western Norway's majestic Aurland Fjord from a height of more than 2,000 feet (610 meters). As you approach the end of the smooth wooden walkway, it plunges downward in front of you as though it were a deadly roller coaster. All that keeps you from plunging with it is a pane of glass. And in the finest tradition of the sublime, it doesn't seem like enough.

Also known as the Stairway to Nothingness, this precarious perch 9,000 feet (2,743 meters) up in the Austrian Alps opened last July. To get there you take a cable car, then pick your way along a narrow and giddily exposed suspension bridge that spans an abyss 1,300 feet (396 meters) deep, and finally descend 14 steps down a cliff face on the Hunerkogel to a glass viewing platform with sweeping views of the Alps stretching away as far as Slovenia and, if you dare to look straight down hundreds of feet, to the Dachstein Glacier below.

Roff Smith writes the blogMy Bicycle and I.