Casa Milà/La Pedrera

Known as 'La Pedrera' or 'The Stone Quarry', this residence was designed by Gaudi and built around 1910.  It was completely unorthodox and very striking.  From the hundreds of arches holding it up to the rambling roof guarded by sentinel like chimneys and hundreds of other modernista touches and organic shapes.

https://en.wikipedia.org/wiki/Casa_Mil%C3%A0

Gaudi devised a system of brick arches, with dimensional form worked out by hanging chains upside down.