Uploaded September 2014 | Updated September 2026, 2 weeks ago

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The bundled tube structure was inspired by a pack of cigarettes. Skidmore, Owings & Merrill structuralengineer Fazlur Khan found bundling building tubes of different heights, resembling cigarettes being pushed out of a pack, meant buildings could be built larger and taller. The bundling and different heights avert the wind and provide for various floor areas. Visit architecture.org/buildings to learn more about Chicago’s most iconic buildings and discover how Chicago’s rich architectural legacy was built.