La Pedrera (Casa Milà)

Casa Milà, universally known by its nickname La Pedrera ("the stone quarry"), was built between 1906 and 1912 for businessman Pere Milà, and it was the last private building Gaudí completed before devoting the rest of his life entirely to the Sagrada Família. Its rippling grey stone facade, undulating like waves or a cliff face, was so radical for its time that critics mocked it mercilessly when it opened — the quarry nickname was originally an insult.

Structurally the building was as revolutionary as it looked: Gaudí used a system of self-supporting stone walls and iron columns with no load-bearing interior walls at all, meaning every floor could be freely partitioned and every apartment given a different layout — an early ancestor of the open-plan office floor, applied to residential architecture decades before it became standard practice. Wrought-iron balconies, made from scrap metal Gaudí is said to have personally selected for its raw, tangled shapes, wind across the entire facade like seaweed.