Art Nouveau Tour of Barcelona. This is Casa Batllo, designed by Gaudi. Spain was not drawn into WW I and as such during that time, had prosperity. As as result, there are over 400 Art Nouveau structures in Barcelona.
Use of Natural Forms: Antoni Gaudi: La Pedrara; This is actually an apartment building in Barcelona, with this amazing rooftop garden and its views of the city as an amenity I wonder if anyone would ever leave ?