http://www.paris-travel-guide.info/eiffel-tower-architectural-style/

Why was the Eiffel Tower designed and built?
Why did Gustave Eiffel design and build the tower? Most of the people in Paris hated the metal tower. Why did Eiffel build it?
+ What is the architectural style of the Eiffel Tower?
It was to show off French engineering and show all the exciting new things one could do with metal frames during the 1889 World Fair. It was considered extremely ugly and functional (remember, metal frames were brand new and considered very pedestrian and functional).
Atomium Belgium