The world keeps growings taller. Standing out has always been the purpose of skyscrapers, and the dimension for this is height. Program, structure, layout, and circulations are strongly conditioned by the vertical dimension. The importance of height is patent in the classification system of the CTBUH (Council on Tall Buildings and Urban Habitat), an international organization founded in 1969 and based in the Illinois Institute of Technology in Chicago, which sets the criteria for measuring the heights of skyscrapers. A distinction is made between the height to tip, which may include antennae or flag poles, and the height of the building up to highest floor, or its height to architectural top, which includes the tower’s needle or crown but not antennae and masts, the usual criterion for classifying skyscrapers. According to this system of measurement, buildings are classified as tall, super-tall (over 300 meters), and mega-tall (over 600 meters). Right now there are three mega-talls and a hundred super-talls in the world. Either at design stage or under construction, another five will pass the 600-meter mark, and two are headed to exceed 1,000 meters...
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