The world's longest bridge is the Danyang–Kunshan Grand Bridge in China, part of the Beijing-Shanghai High-Speed Railway. The bridge, which opened in June 2011, spans 102.4 miles (165 kilometers). Another part of that train line, the 70.8-mile (114-km) long Langfang–Qingxian viaduct, is the second longest bridge in the world.

China constructed the Danyang–Kunshan Grand Bridge in just 4 years, employing 10,000 workers, at a cost of about $8.5 million. It crosses low rice paddies, part of the Yangtze River Delta, with just a few miles of the bridge actually crossing the open water of Yangcheng Lake in Suzhou. The bridge averages about 100 feet (31 meters) off the ground.

More Info: www.livescience.com