Paris in 1887 was a city deeply suspicious of what was about to rise in its center.

A petition was signed by more than three hundred distinguished artists, architects, and writers, protesting what they called "a vertiginously ridiculous tower dominating Paris like a gigantic black factory chimney."

The petition described it as an ink stain over the city. Gustave Eiffel responded: "Do people really think that because one is an engineer, beauty does not concern us in our constructions?"

Built for a World's Fair

The tower was conceived as the centerpiece of the 1889 Exposition Universelle, celebrating the centenary of the French Revolution. Of 700 designs submitted, Eiffel's was unanimously selected.

Two senior engineers in his firm — Maurice Koechlin and Émile Nouguier — had first sketched the idea in 1884: a pylon with four lattice legs rising to meet at the summit, joined by metal trusses at regular intervals. Their original sketch looked almost exactly like what was built.

All 18,038 pieces were fabricated at Eiffel's factory in Levallois-Perret, just outside Paris, machined to an accuracy of one-tenth of a millimetre. The assembly began in July 1887 and was complete twenty-two months later. A team of four men was required for each rivet: one to heat it, one to hold it in place, one to shape the head, and a fourth to hammer it.

Only a third of the 2.5 million rivets were inserted on-site; the rest were pre-assembled at the factory. The construction is said to have caused only one fatality — an extraordinarily low number for a project of this scale and speed.

The Engineering Inside the Curves

Eiffel was a bridge engineer by training, and the tower shows it. He understood wind as the primary challenge for any tall open-air structure and used complex mathematical formulas to calculate the exact curvature of the four legs needed to resist strong gusts.

The resulting lattice design allows wind to pass through rather than push against a solid wall. The tower sways only about nine centimetres in the strongest storms. On hot days, the iron expands and the structure can grow taller by several centimetres — a phenomenon Eiffel accounted for in his calculations.

Saved by the Radio

The tower was originally intended to be dismantled after the 1889 fair. What saved it was wireless communication. Its height made it ideal for radio transmission, and it became a vital strategic communication station during the following decades.

Since then it has accumulated sensors for meteorology, aerodynamics research, and eventually television broadcasting. The Iron Lady, as it's been nicknamed, now receives nearly six million visitors per year — and remains the most visited monument with a paid entrance anywhere on earth.