Starry Night by Vincent Van Gogh. This painting depicts the view outside Van gogh's sanitorium room window at Saint-Rémy-de-Provence, at night. Made even more famous by singer, Don McLean's 1971 song, 'Vincent' (Starry, Starry Night).
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.