So there was this guy named Antoni Gaudi. He designed some buildings in Barcelona in the 1900s. It's gorgeous and mind blowing. People say he was ahead of his time. I think he is in a timeless class of his own.
My favorite was Sagrada Familia, a church, recently upgraded to a basilica a few years ago (by the pope), which is a notch below cathedral (Barcelona already has a cathedral, and each city can only have one). When I walked in, I was overwhelmed. I have never been so moved by architecture.