Sagrada Familia is a building that has been under construction for 140 years and still isn't finished. When you walk inside and see columns branching like trees toward the ceiling, light playing through stained glass in every color, you understand—Antoni Gaudí wasn't creating a temple, but a stone forest reaching toward the sky.

Gaudí's Vision

Gaudí took over the project in 1883 from another architect and completely reimagined it. He devoted the next 43 years of his life to this temple, the final 12 exclusively to it, sleeping in his workshop on the construction site.

His concept: every eleme...