Actually, *all* famous structures needed mathematics, especially in the initial phases of design and construction. Some of the more famous—and exceptionally challenging— buildings include the Chrysler Building in New York (a steel frame skyscraper built around 1930 that was the tallest building in the world before the Empire State Building); the Empire State Building in New York (a steel-framed, stone-clad commercial office skyscraper built in 1931 that rises 1,252 feet [381 meters] high); the Eiffel Tower in Paris, France (designed by architect Gustave Eiffel and built between 1887 and 1889 as a 985-foot-[300-meter-] tall exposition iron observation tower); and the Sears Tower in Chicago (built between 1974 to 1976, it is a steel-frame with glass structure standing at 1,450 feet [442 meters] tall and is, to date, the tallest building in the United States). Places such as the Monterey Aquarium (built around 1980 with reinforced concrete and made compatible with surrounding waterfront structures) also needed mathematics in order to be constructed. Of course, when one gets down to it, *all* types of construction require some math knowledge for them to be built, even a modest piece of cabinetry.

Gustave Eiffel used mathematical concepts to design his famous Eiffel Tower in France between 1887 and 1889.