Construction began on January 26, 1887, and proceeded at a pace that still impresses engineers. Eiffel's company assembled 18,038 pieces of wrought iron, joined by 2.5 million rivets, using detailed shop drawings that ensured each component arrived on site ready to fit. At peak activity, 300 workers swarmed the rising structure. The foundation work took five months; the first level was reached by April 1888; the summit by March 31, 1889 - two years, two months, and five days after the first iron was laid. Remarkably, only one worker died during construction, a man who fell while showing off for his girlfriend after working hours. Eiffel credited the low casualty rate to movable platforms and guard rails, safety measures considered unusual at the time. The total cost came to about 7.8 million francs, roughly 1.5 million under budget.

The tower's original permit allowed it to stand for twenty years. By 1909, it should have been dismantled. What saved the Iron Lady was not sentiment but radio. Eiffel had allowed wireless telegraphy experiments from the summit beginning in 1898, and by the early 1900s the tower had become an indispensable communications platform. The French military used it to intercept German radio signals during World War I, most famously helping to expose the spy Mata Hari. During World War II, when France fell, the elevator cables were cut so that Hitler would have to climb the stairs to hoist his flag - which the Germans never did, settling for a banner at the base. French resistance fighters reactivated the tower's transmitter to broadcast during the liberation of Paris in August 1944.

The tower stands 330 meters tall with its antenna, roughly equivalent to an 81-story building. Its base is square, measuring 125 meters on each side. When it was completed, it surpassed the Washington Monument as the world's tallest human-made structure - a record it held for 41 years until the Chrysler Building overtook it in 1930. The iron lattice weighs approximately 7,300 metric tons, yet the structure exerts only 4.5 kilograms of pressure per square centimeter at its base, about the same as a person sitting in a chair. In extreme heat the iron expands, and the top of the tower can shift up to 18 centimeters away from the sun. Every seven years, 60 tons of paint are applied in three graduated shades - darkest at the base, lightest at the top - to create an illusion of uniform color against the sky.

The Eiffel Tower operates less like a monument and more like a small town turned on its side. Two restaurants occupy the first and second platforms - Le Jules Verne on the second level held a Michelin star for years. A post office on the first level handles mail stamped with a special Eiffel Tower postmark. The summit houses Gustave Eiffel's preserved private apartment, where he once entertained Thomas Edison, as well as meteorological instruments and telecommunications equipment that still serves the city. Two hydraulic elevator systems, original to the 1889 design and among the oldest operating lifts in the world, carry visitors to the second level. A separate system reaches the summit. For those who prefer, 674 steps climb to the second platform. Close to six million people make the trip each year, making it the most visited monument with an entrance fee in the world.

At dusk, 20,000 light bulbs switch on and the tower becomes something else entirely - not an engineering achievement but a signal fire, visible from virtually anywhere in Paris and from aircraft approaching from any direction. The current lighting scheme, installed in 1985 with sodium lamps and enhanced with the sparkling lights added for the millennium celebration in 2000, consumes about 580 megawatt-hours per year. Every hour on the hour after dark, the tower sparkles for five minutes, a display so embedded in Parisian identity that residents claim to set their clocks by it. The tower that Paris once rejected has become the thing Paris cannot imagine being without - a structure so thoroughly identified with its city that seeing it, even from 30,000 feet, means only one thing: you are looking at France.