doors have seven leaves at the top of the opening and four motor-driven horizontal-sliding leaves at the bottom. Among the largest doors ever made, they weigh between 33 and 72 tons (30 and 66 tonnes). The vehicle assembly processes necessitated two 270-ton (250-tonne) bridge cranes that could span almost 150 feet (45 meters), with a hook height of 460 feet (141 meters); the loads they impose upon the foundations are enormous. The structural engineers designed a bed of 4,225,16-inch-diameter (40-centimeter) open-end steel pipe piles, driven 160 feet (49 meters) to bedrock.

In May 1963, the American Bridge Division of U.S. Steel signed a $23.5 million contract for supplying and erecting more than 49,500 tons (45,000 tonnes) of structural steel for the VAB frame completion by 1 December 1964. Six weeks later Blount Brothers Corporation of Montgomery, Alabama, contracted to construct the foundations and floors of the VAB for $8 million. Early in October, bids were invited for general construction: completion of the VAB, site works, roads and utility installations, the VAB utility annex, and the Launch Control Center. The Corps of Engineers, which oversaw all the contracts, set the completion date at 1 January 1966. The bidding was won by a consortium of three California companies—Morrison-Knudsen Company, Perini Corporation, and Paul Hardeman—for almost $63.4 million. The South Gate combine soon took over the VAB structural steel contract and Colby Cranes Manufacturing Company’s contract for the bridge cranes. The consolidated Morrison-Knudsen, Perini, and Hardeman contract was then $88.7 million. The “topping-out” ceremony for the VAB took place on 14 April 1964, although “bricks and mortar” work continued well into 1965.

Further reading

Benson, Charles D., and William Barnaby Faherty. 1978. Moonport: A History of Apollo Launch Facilities and Operations. N.p.: NASA.

Harland, David M. 1998. The Space Shuttle: Roles, Missions, and Accomplishments. Chichester, UK and New York: Wiley.

Jenkins, Dennis R. 1996. The History of Developing the National Space Transportation System: The Beginning through STS-75. Indian Harbor Beach, FL: Dennis R. Jenkins.

Venice, Italy

Venice is one of the world’s densest urban places—a compression of churches, great and small houses, and other buildings crowded around hundreds of piazzi and campi, little relieved with planting and having only two public gardens. Floating on a cluster of more than 100 low islands about 2.5 miles (4 kilometers) off the Veneto region of the Italian mainland, the historical center of this remarkable city is surrounded by the shallow, crescent-shaped Laguna Véneta (Venetian Lagoon) and permeated by a network of over 150 canals, 400 bridges, and countless narrow streets known as calli. It is protected from the Adriatic Sea by the Pallestrina, Lido, and Cavallino littorals, a total of 30 miles (48 kilometers) of narrow strips of sand with seaward entrances to the lagoon. In fact, Venice is built in the sea, hardly a suitable place for a city, and it therefore provides a remarkable example of how humanity rises to meet a challenge.

Why did the city’s founders choose such a location? When he became sole ruler of the Huns in a.d. 446, Attila set out to extend his domain from the River Rhine across the north of the Black Sea to the Caspian Sea. With the Franks and Vandals, five years later he attacked western Europe, only to be driven back by Roman and Visigoth armies. In 452 he invaded Italy, displacing entire communities, many of which fled to islands along the Adriatic coast, then inhabited only by hunters and fishermen. When Attila withdrew a year later the refugees returned to the mainland—but not all. Some historians identify this relocation as the key to the eventual foundation of Venice. After Attila’s death in 453, the Lombards rose to dominate what is now Hungary. Around 568 their king Alboin led an army of Lombards, Gepids, Sarmatians, and others into Italy, overrunning much of the Veneto. He would soon conquer Milan and the Po Valley; Tuscany would follow and, by 575, Rome. The people of the Veneto had again retreated to the lagoons. Because the Lombards remained in Italy, the refugees no longer had homes to which they could return and they remained on the islands. Late in the seventh century their numbers were augmented by more exiles from the harsh Lombard rule.

In the lagoon, a loose confederation of communities emerged, owing allegiance to Byzantium. Each