Gaudi was very fond of nature and nature inspired his work very much. Natural shapes have proven to be effective and tightly linked to efficient structures.

But Gaudi had a weakness: he was a poor mathematician. Yet he wanted to make optimal use of the material in order to be able to transform the freakish and surprisingly fantastical shapes in his head into buildings that could survive weather and storms.

So he found the way that uses some physical properties instead of math to minimize the shearing forces which are the causes of collapses.

One of the shapes he loved was the catenary or chain-line. Chains have a high resistance to an extension force, but no resistance to a shearing force. Being a weak mathematician, Gaudi couldn't make proper calculations.

So, what did he do? He developed simple prototypes. How? He dip a chain into plaster, hang it to dry and then... simply put it upside down.