Picture in your mind the skyline of downtown Toronto. There's the CN Tower1, of course, and the 72-floor First Canadian Place, the city's tallest skyscraper (Figure 1). Cascading from there are the assorted banks and hotels and insurance towers. Now, use your imagination to construct some new buildings, these ones reaching three, four and five times higher than the others. Top it all off with a skyscraper one mile high (three times as high as the CN Tower). Sound fanciful? It did 30 years ago when Frank Lloyd Wright2 proposed the first mile-high building. But not today. The World is now said to be entering the age of the superskyscraper, with tall buildings poised to take a giant new leap into the sky. Skyscrapers approaching the mile mark may still be awhile off, but there are proposals now for megastructures soaring 900 m -- twice as high as the United States" tallest building, the 110-story Sears Tower in Chicago. .

             Suppose that you were asked to erect such a building. How would you do it? What are the obstacles you'd face? What materials would you use? And where would you put it? Well, the first information you would need to know is the kind of land to put this skyscraper on.

             Land.

             When building a superskyscraper, the first thing you would need is a considerable slice of real estate. Tall buildings require a large base to support their load and to keep them stable. In general, the height of a building should be six times its base. For a skyscraper 900-m tall, you'd need a base of 150 square m. That much space is hard to come by in, say, downtown Toronto, forcing you to look for an undeveloped area. Bear in mind that you can not choose a chunk of land with loose sand and silt. .

             Tall buildings must stand on firm ground, or else risk the fate of a structure like the Empress Hotel in Victoria (Figure 2). This grand dowager, completed in 1908, long before the science of soil mechanics, has since found herself slowly sinking into the soft clay.