Art Nouveau was an international style that developed in Europe and North America between 1890-1914. It emphasized organic and flowing forms inspired by nature. The document discusses two examples of Art Nouveau architecture - the 1901 Hotel Van Evelde in Brussels and Antoni Gaudi's Casa Mila in Barcelona. Hotel Van Evelde features a recessed ground floor with upper floors on iron consoles and arched windows with exposed metalwork. Casa Mila, known as the "quarry" for its uneven facade, has an undulating shape inspired by nature like waves or sand dunes that breaks from conventional architecture. Both examples showcase Art Nouveau's emphasis on natural and organic forms.