The Eiffel Tower was designed by Gustave Eiffel’s engineering firm, principally by the engineers Maurice Koechlin and Émile Nouguier. It was built for the 1889 Exposition Universelle, which marked the centennial of the French Revolution. At 300 metres, it was the tallest structure in the world until 1930, and the first to demonstrate that wrought iron could match stone as a monumental material.
The form of the tower follows directly from its structural problem. The four splayed legs trace a parabolic curve that Eiffel calculated as the optimal envelope against wind load, with the moment of force resolved at every height. The base spreads to a 125-metre square and tapers to a square of roughly ten metres at the summit. The elevation is divided by three observation platforms, at 57, 115, and 276 metres, into proportional zones, each smaller and more open than the one beneath it. The wrought-iron lattice that fills the structure is composed of Saint Andrew’s cross bracing within rectangular panels. No element is ornamental, and the visible network is the structural diagram itself. The arches that span between the legs at the first platform are themselves analytic, framing the load path rather than decorating it.
The tower was originally meant to be temporary. Its twenty-year permit expired in 1909, and it survived only because the French Army adopted it as a wireless transmission antenna. A famous petition of 1887, signed by Charles Garnier and Guy de Maupassant among others, had denounced it as a “useless and monstrous” insult to Paris. The retention of the tower marks the moment when Paris accepted that infrastructure could become identity, and that the engineer could claim authorship of monumental form alongside the architect.