Hello, I am a proud neighbour of Barcelona which continues being surprised with Gaudi's architecture. There are nice examples of the catenaries mentioned by Stephanie at the garrets of the Casa Milá (known as La Pedrera) y Casa Batlló, two of his most famous Gaudi's works in Barcelona.

There are many other examples of the use of maths in his buildings like fractals, spirals, conicals, and so; but, of course the better is to follow Stephanies' suggestion and come to Barcelona to see them. You also will find good weather, nice people and good food!