I've lived in Barcelona for one year and I'm used to go there at least one time per year. I've visited all Gaudi's masterpieces (Parque Güell, Palacio Güell and Casa Milá) and also the Casa Batlló that opened for visits very recently. Further, I've been in other houses due to Gaudi in Barcelona (looked only the exterior) and also in the Palacio Episcopal in Leon (Castilla-Leon, Spain). In a single word: spectacular!