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What's the world's longest suspension bridge?

The Bridge That Ingenuity Built

At face value, constructing a suspension bridge to span the Akashi Strait was a no-brainer. Not only would the bridge allow motor vehicle traffic to run between Japan and neighboring Awaji Island for the first time, but Awaji would no longer be the only major island disconnected from the Japanese mainland. Plus, a massive suspension bridge would serve as a testament to Japanese engineering.

There was just one problem: The Akashi Strait was one of the worst places in the world to build a bridge. Few bridge builders wished to master this particular spot because of its strong currents, dense fog and frequent storms that sank hundreds of ships each year. Typhoon winds often ripped through the corridor at more than 280 kilometers (180 miles) an hour. And if that wasn't enough, the strait ran along a major earthquake fault.

Oh, and there was one other pesky issue to consider. No one had ever built a suspension bridge in such cavernous water (the Akashi Strait measured 110 meters -- the equivalent of 360 feet -- deep) or at such an extended length. At its longest point, the bridge would need to be suspended 1,991 meters (6,532 feet) to allow unobstructed access to the shipping lane. To put this in perspective, the main span of San Francisco's Golden Gate Bridge is 1,280 meters (4,200 feet), about two-thirds the length [sources: Cooper, Golden Gate Bridge].

Turns out, the Japanese government was up for the seemingly impossible task. After three decades of planning, followed by 10 years of work by a 2 million-member construction crew, the Akashi Kaikyo Bridge opened in 1998 [sources: Cooper, Ryan]. Its existence is homage to human ingenuity.

The Akashi Kaikyo Bridge, also known as the Pearl Bridge, holds three world records. Its essential span makes it the longest suspension bridge in the world. With two towers standing 80 stories each, it is the tallest suspension bridge on record. And, because it cost 500 billion yen (approximately U.S. $3.6 billion at the time), it was the most expensive suspension bridge built [source: National Geographic].