Erected in Paris for the 1889 World's Fair by Gustave Eiffel's company, the Eiffel Tower is a demonstration of iron engineering; its aesthetic comes from structure displayed openly rather than concealed. On completion it was the tallest human-made structure in the world at 300 metres.

The tower is built by joining some 18,000 separate wrought-iron pieces with 2.5 million rivets. The structural element is the lattice girder: instead of a solid mass, an open iron web woven from triangles. This open texture has two reasons. The first is weight: using lattice instead of solid iron dramatically reduces material and therefore weight — the 300-metre tower weighs only 7,300 tonnes. The second is wind: Eiffel's real engineering problem was not gravity but wind pressure. The curved profile of the four legs, splaying wide below and gathering toward the top, was calculated mathematically to distribute wind force to the ground; the open lattice lets the wind pass through.

For this reason the tower has no "facade" or ornament; what is seen is the load-bearing system itself. Contemporary artists found it ugly and protested, but the tower is modern precisely for this: structure is no longer hidden behind a skin but becomes the expression of the architecture. The Eiffel Tower thus turns iron-lattice engineering into an aesthetic principle.