Tour Eiffel

The structure was built between 1887 and 1889 as the entrance arch for the Exposition Universelle, a World’s Fair marking the centennial celebration of the French Revolution.

At the time the tower was built many people were shocked by its daring shape. But the shape of the tower was determined by mathematical calculation involving wind resistance.

The structure of the Eiffel Tower weighs 7,300 tons. Depending on the ambient temperature, the top of the tower may shift away from the sun by up to 18 cm (7 in), due to thermal expansion of the metal on the side facing the sun. The tower also sways 6-7 cm (2-3 in) in the wind. Including the 24 m (79 ft) antenna, the structure is 324 m (1,063 ft) high (since 2000), which is equivalent to about 81 levels in a conventional building.

It is the symbol of Paris and is the most visited paid monument in the world per year.

Since the beginning of the 20th century, the tower has been used for radio transmission. Until the 1950s, an occasionally modified set of antenna wires ran from the summit to anchors on the Avenue de Suffren and Champ de Mars. They were connected to long-wave transmitters in small bunkers; in 1909, a permanent underground radio center was built near the south pillar and still exists today.

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