This extraordinary building, former home of banker Javier González Longoria (and also known as Palacio Longoria), is the only example of Catalan Art Nouveau architecture in Madrid. Gaudí and other exponents of this distinctive style never really got a look in, probably because of the fierce rivalry between the Spanish capital and Barcelona. Designed at the beginning of the century by José Grases Riera in a style that also shows French influence, the building bears more than a passing resemblance to an exotic fairy-tale sand castle. Today it's home of the Association of Spanish Writers and Artists; and though it's not open to the public, the unique exterior alone is well worth a look.