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Sears Tower Megastructure Documentary Download Willis Tower (formerly named, but still commonly referred to as, Sears Tower ) is a 108-story, 1451-foot (442 m) skyscraper in Chicago, Illinois. At the time of its compl etion in 1974, it was the tallest building in the world, surpassing the World Trade Center towers in New York, and it held this rank for nearly 25 years. The Willis Tower is the tallest building in the United States and the fifth-tallest freestanding structure in the world, as well as the fifth tallest building in the world to the roof. For 20 years, the Sears Tower held the record for the world�s tallest building. Completed in 1974, the 108 stories high building is almost half a kilometer tall. And it still holds the record for having the world�s highest antenna. John Zils, structural engineer and designer of this mega-structure shares some of the secrets about the tower. And get a behind-the-scenes look at some of the various systems and controls that are vital t...

The Channel Tunnel ( is a 50.5-kilometre (31.4 mi) undersea rail t unnel linking Folkestone , Kent in the United Kingdom with Coquelles, Pas-de-Calais near Calais in northern France beneath the English Channel at the Strait of Dover. At its lowest point, it is 75 metres (250 ft) deep. [ 3 ] [ 4 ] [ 5 ] At 37.9 kilometres (23.5 mi), the Channel Tunnel posses ses th e longest undersea portion of any tunnel in the world, although the Seikan Tunnel in Japan is both longer overall at 53.85 kilometres (33.46 mi), and deeper at 240 metres (790 ft) below sea level. A tunnel connecting Britain and France has been an engineering holy grail since the early 19th century. The first attempt at a tunnel excavation began in 1880, but the project was abandoned soon after and workings lay dormant for a hundred years. In 1988, international treaties were signed and once more excavation work began in earnest. At 50km from Kent to Normandy, with a full 39km passing 40m under the English Chann...