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Gustave Eiffel's primary expertise was civil engineering, which is the design, construction, and maintenance of the built environment, including roads, bridges, dams, airports, tunnels, power plants, and water treatment plants. He is best known for his work on the Eiffel Tower, which was built for the 1889 World's Fair in Paris. The tower is a wrought iron lattice tower that is 324 meters (1,063 feet) tall.