by Kate Ascher

When it comes to buildings, size matters — more so today than ever before. Look up in the heart of any of the world's major cities and your eyes will likely alight upon a towering, glass-walled structure — if not literally scraping the sky, then certainly pointing in that direction.

The proliferation of skyscrapers is accelerating rapidly. Prior to the year 2000, fewer than 250 buildings around the world reached higher than 600 feet (180 meters); between 2000 and 2009, that number more than doubled.

And it continues to grow faster than ever before: at the beginning of 2010, almost 400 new skyscrapers were under construction around the world. The downturn in the global economy that began in 2008 did little to dent the world's appetite for tall buildings.

Not only are there more tall buildings, but they are in more places. Once a purely American phenomenon, the construction of skyscrapers is now very much a global one. Of the 38 skyscrapers over 600 feet (180 meters) completed in 2009, 22 of them were in Asia and seven were in the Middle East. The "tallest" metropolis in the world is in Asia: the combined height of Hong Kong's skyscrapers is roughly three times that of New York City's.

So prolific are these towers today in the world's metropolises, and so enthusiastic are their planners, that there are now adjectives that differentiate between them: "tall" is often used to describe skyscrapers between 500 and 1,000 feet (150 to 300 meters); anything above that is considered "supertall." Even measuring the building is now a science: do you measure it from street level or from the basement? To the highest occupied floor or to the top of its crown?

Some readers may wonder why we should care how tall these towers are or how many of them exist. Are they not just the product of speculation and greed on the part of a handful of wealthy developers? Or the modern incarnation of some age-old form of civic pride? The answer is no — they are much more than that.   >>>

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SUBSCRIPTION SAMPLE Skyscraper construction has been on the rise in recent years, and many of the new skyscrapers are being built in Middle Eastern and Asian cities, such as Shanghai, China. Image does not appear in book. Photo: Flickr user Jeff Extra Large Image SUBSCRIPTION SAMPLE Although Manhattan (pictured) is one of the densest urban areas in North America, the combined height of Hong Kong's skyscrapers is roughly three times that of New York City's. Image does not appear in book. Photo: Flickr user Chris Extra Large Image   Click on thumbnail images to view full-size pictures.