The Eiffel Tower was meant to be demolished after 20 years but was saved by its use as a massive radio antenna.

The Eiffel Tower was the centerpiece of the 1889 Exposition Universelle, marking the centennial of the French Revolution. The contract signed by the City of Paris and Gustave Eiffel granted a land concession for only 20 years, after which ownership would revert to the city and the structure would be dismantled. To prevent this, Eiffel encouraged experiments in meteorology and aerodynamics, but it was wireless telegraphy that ultimately secured the tower's future.In 1898, Eugene Ducretet conducted the first wireless telegraphy trials between the tower and the Pantheon, a distance of 4 kilometers. By 1903, Eiffel offered the tower to the French military for further radio experiments, leading to the installation of a permanent station in 1906. This decision proved decisive during World War I, specifically in September 1914 during the Battle of the Marne. The tower's transmitters intercepted German radio messages that revealed their troop movements, allowing the French to launch a successful counter-attack.The tower also played a role in capturing the famous spy Mata Hari by intercepting her coded messages. In 1910, the City of Paris renewed the tower's concession for another 70 years due to its strategic importance. Today, the tower stands at 330 meters tall, which includes the height of the numerous digital television and radio antennas mounted at its peak. It continues to serve as a vital transmission site for the Ile-de-France region, hosting over 120 different antennas.